Timing reproducing device and demodulator

ABSTRACT

In-phase and orthogonal components of a base band signal having a preamble symbol are squared to obtain squared in-phase orthogonal components. Amount of correlation is obtained between the squared in-phase component and a ½ symbol frequency component output from a VCO or an oscillator, and amount of correlation is obtained between the squared orthogonal component and the ½ symbol frequency component. Finally, a phase control signal for carrying out a phase control is generated by using the obtained amount of correlations.

TECHNICAL FIELD

The present invention relates to a demodulator and a timing regeneratingdevice that is used in this demodulator.

BACKGROUND ART

As a conventional system of timing regeneration for a demodulator of abroadband digital radio communication system having a preamble signalanalysis function, there has been one as described in Japanese PatentApplication Laid-Open No. 8-46658.

This system focuses on the fact that the preamble signal has ½ of thefrequency component of the symbol frequency (fs). Based on this, acorrelation is obtained at the receiver side between the preamble signaland a ½ symbol frequency component exp[−jπ(fs)t] output from a VCO(Voltage Control Oscillator). A timing phase is estimated from a vectorangle of this correlation value.

Further, according to this system, sampling speed (i.e. sample/symbol)of the data is only 2. In the mean time, Japanese Patent ApplicationLaid-Open No. 6-141048 discloses a system of estimating a timing phasefrom a correlation between a signal (for example, an envelope) after anonlinear processing and a symbol frequency component exp [−j2π(fs)t].According to this system, minimum value of a necessary sampling speed is4. Therefore, the sampling speed in the system described in JapanesePatent Application Laid-Open No. 8-46658 is ½ of that disclosed inJapanese Patent Application Laid-Open No. 6-141048. As a result, it ispossible to realize low power consumption of the receiver.

FIG. 20 is a structure diagram of a demodulator including a timingregenerating device that is similar to the demodulator described in theJapanese Patent Application Laid-Open No. 8-46658.

This demodulator mainly consists of antenna 100, frequency convertingunit 200, first A/D converter 300 a, second A/D converter 300 b, timingregenerating device 400, and data deciding unit 500.

The timing regenerating device 400 includes VCO 401, timing phasedifference calculating unit 402, Ich correlation calculating unit 403,Qch correlation calculating unit 404, and vector combination selectingunit 405.

Detailed structure of the vector combination selecting unit 405 will beexplained with reference to FIG. 21.

The vector combination selecting unit 405 mainly consists of firstvector combining unit 406 a, second vector combining unit 406 b, thirdvector combining unit 406 c, fourth vector combining unit 406 d, maximumabsolute value detecting unit 407, and selecting unit 408.

How this demodulator demodulates a received preamble signal will beexplained now.

First, the antenna 100 receives the preamble symbol of RF band. Thefrequency converting unit 200 frequency converts this preamble symbol ofthe RF band into a preamble symbol of a base band.

FIG. 22 is a signal space diagram showing a preamble symbol of this baseband (for example, a “1001” pattern in the QPSK conversion system). InFIG. 22, θc denotes, in degrees, a carrier phase of a reception signal.The preamble symbol shifts between a Nyquist point “A” and a Nyquistpoint “B” alternately through the origin for each one symbol in thedrawing.

The vector angle of the Nyquist point “A” is θc, and the vector angle ofthe Nyquist point “B” is (θc+180). Difference between the vector anglesof the Nyquist point “A” and the Nyquist point “B” is 180 degree.

The first A/D converter 300 a receives the preamble symbol of the baseband, samples the in-phase component of the preamble symbol at timet=τ+iT/2 (where i=1, 2, 3, . . . , and τ represents a timing error(−T/2≦τ<T/2), and T represents a symbol frequency), and outputs asampled preamble data string Ip_(i) (i=1, 2, 3, . . . ).

Similarly, the second A/D converter 300 b receives the preamble symbolof the base band, samples the orthogonal component of the preamblesymbol at the time t=τ+iT/2, and outputs a sampled preamble data stringQp_(i) (i=1, 2, 3, . . . ). The first A/D converter 300 a and the secondA/D converter 300 b sample the data based on a sampling clock outputfrom the timing regenerating device 400.

The timing regenerating device 400 calculates a timing error τ by usingthe sampled preamble data strings Ip_(i) and Qp_(i) (i=1, 2, 3, . . . ),and carries out a phase control for canceling the timing error τ to aregeneration sample clock and a regeneration symbol clock. Theregeneration symbol clock is a clock of a symbol period having theregeneration sample clock frequency-divided into two.

The data deciding unit 500 receives the significant random data stringsId_(i) and Qd_(i) (i=1, 2, 3, . . . ) that follow the preambles afterthe timing error τ has been cancelled by the timing regenerating device400, and latches the data at the Nyquist points by the regenerationsymbol clock. Then, the data deciding unit 500 decides the data usingthe latched Nyquist point data, and outputs the demodulated data.

Detail operation of the timing regenerating device 400 will be explainednow. First, the Ich correlation calculating unit 403 obtains correlationbetween each of the in-phase component I (t) and the orthogonalcomponent Q (t) of the preamble symbol shown in FIG. 22 and a frequencycomponent exp[−jπ(fs)t] that is ½ of the symbol frequency, respectively.Specifically, the Ich correlation calculating unit 403 performs thecalculation shown in the equations (1a) and (1b) with respect to theover-sampled preamble data string Ip_(i) (i=1, 2, 3, . . . ):

Ic _(i) =Ip _(i)×cos πi/2  (1a)

Is _(i) =Ip _(i)×sin πi/2  (1b)

Then, the Ich correlation calculating unit 403 calculates an average ofthe obtained results (Ic_(i), Is_(i)), thereby to obtain correlationvalues (CI, SI). Further, the Qch correlation calculating unit 404performs the calculation shown in the equations (2a) and (2b) withrespect to the over-sampled preamble data string QP_(i) (i=1, 2, 3, . .. ) in a similar manner:

Qc _(i) =Qp _(i)×cos πi/2  (2a)

Qs _(i) =Qp _(i)×sin πi/2  (2b)

Then, the Qch correlation calculating unit 404 calculates an average ofthe obtained results (Ic_(i), Is_(i)), thereby to obtain correlationvalues (CQ, SQ).

In the equations (1a), (1b), (2a), and (2b), cos πi/2=1, 0, −1, 0, . . ., and sin πi/2=0, 1, 0, −1, . . . . Therefore, it is easy to obtain thecorrelation values (CI, SI) and (CQ, SQ). For example, when averagingwith four symbols, the correlation values (CI, SI) can be obtained fromthe equations (3a) and (3b) as follows:

CI=(Ip _(i) −Ip _(i+2) +Ip _(i+4) −Ip _(i+6) +Ip _(i+8) −Ip _(i+10) +Ip_(i+12) −Ip _(i+14))/8  (3a)

SI=(Ip _(i+1) −Ip _(i+3) +Ip _(i+5) −Ip _(i+7) +Ip _(i+9) −Ip _(i+11)+Ip _(i+13) −Ip _(i+15))/8  (3b)

Correlation values (CQ, SQ) can be obtained from the equations (4a) and(4b) as follows:

CQ=(Qp _(i) −Qp _(i+2) +Qp _(i+4) −Qp _(i+6) +Qp _(i+8) −Qp _(i+10) +Qp_(i+12) −Qp _(i+14))/8  (4a)

SQ=(Qp _(i+1) −Qp _(i+3) +Qp _(i+5) −Qp _(i+7) +Qp _(i+9) −Qp _(i+11)+Qp _(i+13) −Qp _(i+15))/8  (4b)

The vector angle between the correlation values (CI, SI), and the vectorangle between the correlation values (CQ, SQ) both indicate timing phaseerrors. However, depending on the carrier phase θc, both the vectors maybe pointed in the same direction, opposite directions, or one vector mayhave a value equal to zero.

For example, for the preamble symbols at A and B that satisfy the rangeof θc as (90<θc<180) or (270<θc<360) as shown in FIG. 22, when the Ichcorrelation calculating unit 403 samples at the timings of verticallines shown in FIG. 23(a) and also when the Qch correlation calculatingunit 404 samples at the timings of vertical lines shown in FIG. 23(b),data strings {Ip_(i), Ip_(i+1), Ip_(i+2), Ip_(i+3), . . . } and datastrings {Qp_(i), Qp_(i+1), Qp_(i+2), Qp_(i+3), . . . } are obtainedrespectively. In this case, the correlation values (CI, SI) and (CQ, SQ)as shown in FIG. 24 are obtained, and the correlation vectors arepointed in opposite directions.

On the other hand, for the preamble symbols that satisfy the range of θcas (0<θc<90) or (180<θc<270) as shown in FIG. 25, when the Ichcorrelation calculating unit 403 samples at similar timings as those inFIG. 23, that is, at timings of vertical lines shown in FIG. 26(a) andalso when the Qch correlation calculating unit 404 samples at thetimings of vertical lines shown in FIG. 26(b), data strings {Ip_(i),Ip_(i+1), Ip_(i+2), Ip_(i+3), . . . } and data strings {Qp_(i),Qp_(i+1), Qp_(i+2), Qp_(i+3), . . . } are obtained respectively. In thiscase, two correlation values of the correlation values (CI, SI) andcorrelation values (CQ, SQ) as shown in FIG. 27 are obtained, and thecorrelation vectors point toward the same direction.

Further, it is also clear that each vector length changes depending onthe carrier phase θc. When θc={0, 180}, the vector corresponding to thecorrelation values (CI, SI) has a value equal to zero, and when θc={90,−90}, the vector corresponding to the correlation values (CQ, SQ) has avalue equal to zero.

The vector combination selecting unit 405 receives the correlationvalues (CI, SI) and (CQ, SQ), and combines them in four statusesrespectively in order to reduce the influence of the carrier phase θc.Then, the vector combination selecting unit 405 selects a combinedvector having the highest SN ratio. The timing phase differencecalculating unit 402 receives this combined vector, and calculates atiming phase.

Next, detail operation of the vector combination selecting unit 405 willbe explained with reference to FIG. 21. The maximum absolute valuedetecting unit 407 obtains four absolute values of CI, CQ, SI and SQ ofthe correlation values (CI, SI) and (CQ, SQ), and detects a maximum ofthese the four absolute values.

The first vector combining unit 406 a outputs combined vectors (G1c,G1s) based on following equations (5a) and (5b):

G1c=CI+sign[CI]·|CQ|  (5a)

G1s=SI+sign[CI·CQ]·|SQ|  (5b)

The second vector combining unit 406 b outputs combined vectors (G2c,G2s) based on following equations (6a) and (6b):

G2c=CQ+sign[CQ]·|CI|  (6a)

G2s=SQ+sign[CI·CQ]·|SI|  (6b)

The third vector combining unit 406 c outputs combined vectors (G3c,G3s) based on following equations (7a) and (7b):

G3c=CI+sign[SI·SQ]·|CQ|  (7a)

G3s=SI+sign[SI]·|SQ|  (7b)

The fourth vector combining unit 406 d outputs combined vectors (G4c,G4s) based on following equations (8a) and (8b):

G4c=CQ+sign[SI·SQ]·|CI|  (8a)

G4s=SQ+sign[SQ]·|SI|  (8b)

In the above equations, the sign [*] expresses a sign {−1, +1} of anumerical value within the brackets.

The selecting unit 408 receives a detection signal of the maximumabsolute value detecting unit 407, and sets combined correlation values(ΣC, ΣS) as shown in following equations (9a), (9b), (9c), and (9d)respectively according to the status of a maximum value of the absolutevalues:

(ΣC, ΣS)=(G1c, G1s) (when |CI| is maximum)  (9a)

(ΣC, ΣS)=(G2c, G2s) (when |CQ| maximum)  (9b)

(ΣC, ΣS)=(G3c, G3s) (when |SI| is maximum)  (9c)

(ΣC, ΣS)=(G4c, G4s) (when |SQ| is maximum)  (9d)

Based on the above processing, the influence of the carrier phase θc isremoved, and the combined vector having the vector represented by thecorrelation values (CI, CQ) and (SI, SQ) set to the same direction isselected as a vector most suitable for estimating a timing phase.

For example, in the case of FIG. 24, the correlation values (CQ, SQ)having a smaller vector length are inverted to set both vectordirections to the same direction, and the inverted correlation values(CQ, SQ) are added to the correlation values (CI, SI). Then, thiscombined vector is selected. In this case, the combined correlationvalues (ΣC, ΣS) become as shown in FIG. 28. In the case of FIG. 27, thecorrelation values (CQ, SQ) having a smaller vector length are addeddirectly to the correlation values (CI, SI). Then, this combinedvectoris selected. In this case, the combined correlation values (ΣC, ΣS)become as shown in FIG. 29.

It is also possible to structure the vector combination selecting unit405 as shown in FIG. 30. In the case of the vector combination selectingunit 405 shown in FIG. 30, the vector combination selecting unit shownin FIG. 21 does not select one vector from the four vectors generated inadvance from CI, SI, CQ and SQ. In stead, the vector combinationselecting unit 405 selectively adds a result of first selecting unit 406a, a result of second selecting unit 406 b, a result of third selectingunit 406 c, and a result of fourth selecting unit 406 d, based on adetection result of the maximum absolute value detecting unit 407. Inthis structure, it is possible to reduce the circuit scale as comparedwith the structure of FIG. 21. In FIG. 30, 409 a denotes first adder,and 409 b denotes second adder.

Next, the operation of the vector combination selecting unit 405 shownin FIG. 30 will be explained. First, the respective selecting unitoutput values of SEL1, SEL2, SEL3, and SEL4, based on the detectionresult of the maximum absolute value detecting unit 407. The details areas follows.

SEL1 output by the first selecting unit 406 a has a value as representedby the following equations (10a) and (10b):

SEL 1 =CI (when |CI| or |SI| is maximum)  (10a)

SEL 1 =CQ (when |CQ| or |SQ| is maximum)  (10b)

SEL2 output by the first selecting unit 406 b has a value as representedby the following equations (11a), (11b), (11c), and (11d):

SEL 2=sign[CI]·|CQ| (when |CI| is maximum)  (11a)

SEL 2=sign[CQ]·|CI| (when |CQ| is maximum)  (11b)

SEL 2=sign[SI·SQ]·|CQ| (when |SI| is maximum)  (11c)

SEL 2=sign[SI·SQ]·|CI| (when |SQ| is maximum)  (11d)

SEL3 output by the third selecting unit 406 c has a value as representedby the following equations (12a), (12b), (12c), and (12d):

 SEL 3=sign[CI·CQ]·|SQ| (when |CI| is maximum)  (12a)

SEL3=sign[CI·CQ]·|SI| (when |CQ| is maximum)  (12b)

SEL3=sign[SI]·|SQ| (when |SI| is maximum)  (12c)

SEL 3=sign[SQ]·|SI| (when |SQ| is maximum)  (12d)

SEL4 output by the fourth selecting unit 406 d has a value asrepresented by the following equations (13a) and (13b):

SEL 4 =SI (when |CI| or |SI| is maximum)  (13a)

SEL 4 =SQ (when |CQ| or |SQ| is maximum)  (13b)

The outputs SEL1 and SEL2 of the selecting units 406 a and 406 b isinput into the first adder 109 a. The outputs SEL3 and SEL4 of theselecting units 406 c and 406 d is input into the second adder 109 b.The first adder 409 a adds the values of SEL1 and SEL2, and outputs aresult of the addition as ΣC. The second adder 409 b adds the values ofSEL3 and SEL4, and outputs a result of the addition as ΣS.

Thus, the vector combination selecting unit 405 shown in FIG. 30 outputsvalues similar to those of the vector combination selecting unit 405having the structure shown in FIG. 21.

The timing phase difference calculating unit 402 receives the combinedcorrelation values (ΣC, ΣS) obtained by the vector combination selectingunit shown in FIG. 21 and FIG. 30, and obtains the vector angle shown bythe correlation values (ΣC, ΣS) based on the following equation (14):

θ_(2s)=tan⁻¹(ΣS/ΣC)  (14)

where θ_(2s) represents a timing phase difference when normalization iscarried out in the two-symbol period (2T). Therefore, when normalizationis carried out in the symbol period (T), the timingphase difference θs[deg] is obtained from the equation (15):

θs=2θ_(2s) mod 360  (15)

There is a difference of 180 [deg] between θ_(2s) shown in FIG. 28 andθ_(2s) shown in FIG. 29. However, based on the processing of theequation (15), the θs obtained from the θ_(2s) in FIG. 28 and the θsobtained from the θ_(2s) in FIG. 29 coincide with each other.

The relationship between the timing phase difference θs and the timingerror τ is as shown in the equations (16a) and (16b). When θs>180 [deg],

τ=(θs−360)T/360  (16a),

and when θs≦180 [deg],

τ=(θs)T/360  (16b)

The timing phase difference calculating unit 402 gives a phase controlsignal for canceling the timing error τ to the VCO 401 at the latterstage, based on the timing error τ obtained using the equations (16a)and (16b).

The VCO 401 receives the phase control signal from the timing phasedifference calculating unit 402, controls phases of the regenerationsample clock and the regeneration symbol clock, and sets the timingerror τ to “0”. The regeneration symbol clock is generated based on thefrequency division into two of the regeneration sample clock that hasbeen phase-controlled by the control signal, for example.

As explained above, the conventional timing regenerating device 400using the preamble calculates correlation between the ½ symbol frequencycomponent included in the preamble symbol and the ½ symbol frequencycomponent exp[−jπ(fs)t] output from the VCO 401, and then estimates atiming phase from the vector angle shown by the correlation values.Further, as the sampling speed is a low speed of 2 [sample/symbol], thisis an effective method particularly for the broadband TDMA radiocommunication system.

Although the vector combination selecting unit 405 reduces the influenceof the carrier phase θc, this timing regenerating device has had aproblem that the precision of the calculation in the timing error τ iscontrolled by the carrier phase θc.

In other words, the magnitude of the combined correlation values (ΣC,ΣS) output from the vector combining unit 405 becomes largest when thecarrier phase θc is {45, 135, 225, 315} [deg], and becomes smallest whenthe carrier phase θc is {0, 90, 180, 270} [deg]. The ratio of thesemagnitudes becomes 2^(1/2):1. Therefore, there arises such a phenomenonthat the precision in the calculation of the timing error τ becomes bestwhen the carrier phase θc is {45, 135, 225, 315} [deg], and becomesworst when the carrier phase θc is {0, 90, 180, 270} [deg].

When the preamble symbol having the carrier phase θc=45 [deg] as shownin FIG. 31 is received at the timings of the vertical lines shown inFIG. 32, for example, the amplitude of the I component and the amplitudeof the Q component of the preamble symbol becomes the same value(1/(2^(1/2)) of an envelope level, where the envelope level is a radiusof a circle of the signal space diagram shown in FIG. 32). Therefore,the correlation values (CI, SI) at the I component side and thecorrelation values (CQ, SQ) at the Q component side become the samemagnitude. The combined correlation values (ΣC, ΣS) in this case becomethe values obtained by synthesizing the correlation values (CI, SI) atthe I component side with the correlation values (CQ, SQ) at the Qcomponent side, as shown in FIG. 33(a)

On the other hand, when the preamble symbol having the carrierphaseθc=90 [deg] as shownin FIG. 34 is received at the timings of thevertical lines shown in FIG. 35, for example, the amplitude of the Icomponent of the preamble symbol becomes “0”, and the amplitude of the Qcomponent of the preamble symbol becomes the envelope level. Therefore,the correlation values (CI, SI) at the I component side becomes “0”, andthe correlation values (CQ, SQ) at the Q component side become 2_(1/2)times the correlation values when θc=45 [deg]. The combined correlationvalues (ΣC, ΣS) in this case become the correlation values (CQ, SQ) atthe Q component side because the correlation values (CI, SI) at the Icomponent side becomes “0”, as shown in FIG. 33(b).

As a result, the ratio of the magnitude of the combined correlationvalues (ΣC, ΣS) when θc=45 [deg] to the magnitude of the combinedcorrelation values (ΣC, ΣS) when θc=90 [deg] becomes 2^(1/2):1.Therefore, it is clear that the SN ratio of the combined correlationvalues (ΣC, ΣS) when θc=45 (or 125, 225, 315) [deg] becomes higher thanthe SN ratio of the combined correlation values (ΣC, ΣS) when θc=90 (or0, 180, 270) [deg]. Accordingly, in the conventional system, theprecision in the calculation of the timing error τ when θc=45 (or 125,225, 315) [deg] becomes higher than the precision in the calculation ofthe timing error τ when θc=90 (or 0, 180, 270) [deg].

Further, according to the conventional timing regenerating device, whenthe preamble symbol has a ½ symbol frequency component like the preamblesymbol that shifts by ±90 [deg] at every one symbol as shown in FIG. 36,in addition to the preamble symbol that shifts by ±180 [deg] at everyone symbol as shown in FIG. 22, for example, it is possible to estimatea timing phase from any signal. However, in this case, there has alsobeen a problem that the precision in the calculation of the timing errorτ is influenced by the carrier phase θc.

Further, the conventional timing regenerating device is effective onlywhen the reception timing of a timing phase is known. For example, whenthe reception timing of a burst signal at the time of turning on thepower supply to the mobile terminal or at the line reconnection timeafter recovery from a shadowing is unknown, it is not possible to knowthe reception timing of a preamble symbol. Therefore, it has not beenpossible to apply the conventional timing regenerating device.

It is an object of the present invention to provide a demodulatorcapable of calculating a timing error at high precision withoutreceiving an influence of a carrier phase θc.

Further, it is another object of the present invention to provide ademodulator that becomes valid when the reception timing of a preambleis not known, by simultaneously realizing an estimation of a timingphase using a preamble and a detection of the preamble.

Further, it is still another object of the present invention to providea demodulator that realizes a high-speed synchronization and ahigh-speed resynchronization in a short preamble without receiving aninfluence of a carrier phase, and realizes a satisfactory BER (bit-errorratio) characteristics in a significant data section that follows thepreamble, even when the reception timing of a burst signal that occursat the power supply start-up time or at the reconnection timing after arecovery from a shadowing is unknown.

DISCLOSURE OF THE INVENTION

The timing regenerating device according to one aspect of the presentinvention comprises an in-phase component square calculation unit thatreceives a base band signal having a preamble symbol, calculates squareof an in-phase component of the base band signal and outputs the squaredin-phase component; an in-phase multiplier that multiplies a sign bit(±1) of the in-phase component of the base band signal to the squaredin-phase component and outputs the result as signed squared in-phasecomponent; an orthogonal component square calculation unit that receivesthe base band signal, calculates square of an orthogonal component ofthe base band signal and outputs the squared orthogonal component; anorthogonal multiplier that multiplies a sign bit (±1) of the orthogonalcomponent of the base band signal to the squared orthogonal componentand outputs the result as a signed squared orthogonal component; asquared-preamble in-phase correlation calculating unit that calculatescorrelation value between the signed squared in-phase component and a ½symbol frequency component, and outputs the correlation value as anin-phase correlation signal; a squared-preamble orthogonal correlationcalculating unit that calculates correlation value between the signedsquared orthogonal component and the ½ symbol frequency component, andoutputs the correlation value as an orthogonal correlation signal; avector combination selecting unit that compares the magnitude of thein-phase correlation signal with the magnitude of the orthogonalcorrelation signal, matches the direction of a vector shown by thein-phase correlation signal or the orthogonal correlation signalwhichever is smaller to the direction of a vector shown by the in-phasecorrelation signal or the orthogonal correlation signal whichever islarger, combines these signals, and outputs a correlation signal afterthe combination as a combined correlation signal; and a timing phasedifference calculating unit that outputs a phase control signal from avector angle shown by the combined correlation signal.

The timing regenerating device according to one aspect of the presentinvention comprises an in-phase component square calculation unit thatreceives a base band signal having a preamble symbol, calculates squareof an in-phase component of the base band signal and outputs the squaredin-phase component; an in-phase multiplier that multiplies a sign bit(±1) of the in-phase component of the base band signal to the squaredin-phase component and outputs the result as signed squared in-phasecomponent; an orthogonal component square calculation unit that receivesthe base band signal, calculates square of an orthogonal component ofthe base band signal and outputs the squared orthogonal component; anorthogonal multiplier that multiplies a sign bit (±1) of the orthogonalcomponent of the base band signal to the squared orthogonal componentand outputs the result as a signed squared orthogonalcomponent; asquared-preamble in-phase correlation calculating unit that calculatescorrelation value between the signed squared in-phase component and a ½symbol frequency component, and outputs the correlation value as anin-phase correlation signal; a squared-preamble orthogonal correlationcalculating unit that calculates correlation value between the signedsquared orthogonal component and the ½ symbol frequency component, andoutputs the correlation value as an orthogonal correlation signal; avector combination selecting unit that compares the magnitude of thein-phase correlation signal with the magnitude of the orthogonalcorrelation signal, matches the direction of a vector shown by thein-phase correlation signal or the orthogonal correlation signalwhichever is smaller to the direction of a vector shown by the in-phasecorrelation signal or the orthogonal correlation signal whichever islarger, combines these signals, and outputs a correlation signal afterthe combination as a combined correlation signal; and a preambledetecting/timing phase difference calculating unit that calculates avector angle and a vector length of the combined correlation signal,decides that the preamble symbol has been detected when the vectorlength is larger than a predetermined threshold value, calculates atiming phase difference using a vector angle shown by the combinedcorrelation signal at that time, and outputs a phase control signal.

Further, according to still another aspect of the invention, in thetiming regenerating device of the above aspect, the timing regeneratingdevice comprises a VCO that outputs a regeneration symbol clock, aregeneration sample clock, and a ½ symbol frequency component, based ona phase control signal. The base band signal to be input into thein-phase component square calculation unit and the orthogonal componentsquare calculation unit is a signal that has been sampled based on theregeneration sample clock. The squared-preamble in-phase correlationcalculating unit calculates correlation value using the ½ symbolfrequency component output from the VCO, and the squared-preambleorthogonal correlation calculating unit calculates correlation valueusing the ½ symbol frequency component output from the VCO.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises a phasedetecting unit that detects advancement/delay of a timing phase usingthe base band signal sampled based on the regeneration sample clock, andoutputs detected signals as phase detection signals; and a phasedetection signal averaging unit that calculates an average of the phasedetection signals, and outputs the average as a phase advance/delaysignal. The VCO outputs a regeneration symbol clock, a regenerationsample clock, and a ½ symbol frequency component, based on the phasecontrol signal and the phase advance/delay signal.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises an oscillatorthat outputs an asynchronous sample clock and a ½ symbol frequencycomponent. The base band signal to be input into the in-phase componentsquare calculation unit and the orthogonal component square calculationunit is a signal that has been sampled by the asynchronous sample clock.The squared-preamble in-phase correlation calculating unit calculatescorrelation value using the ½ symbol frequency component output from theoscillator, and the squared-preamble orthogonal correlation calculatingunit calculates correlation value using the ½ symbol frequency componentoutput from the oscillator.

Also, the timing phase difference calculating unit calculates a timingphase difference from a squared root of the in-phase component of acombined correlation signal and a vector angle shown by a squared rootof an orthogonal component of the combined correlation signal.

Further, according to still another aspect of the invention, in thetiming regenerating device of the above aspect, the preambledetecting/timing phase difference calculating unit calculates a timingphase difference from a vector angle shown by a value obtained bymultiplying a sign {±1} of the in-phase component to a square root of anabsolute value of an in-phase component of a combined correlation signaland a value obtained by multiplying a sign {±1} of the orthogonalcomponent to a square root of an absolute value of an orthogonalcomponent of the combined correlation signal.

Further, the timing regenerating device according to still anotheraspect of the invention comprises an in-phase component squarecalculation unit that receives a base band signal having a preamblesymbol, calculates square of an in-phase component of the base bandsignal and outputs the squared in-phase component; an in-phasemultiplier that multiplies a sign bit (±1) of the in-phase component ofthe base band signal to the squared in-phase component and outputs theresult as signed squared in-phase component; an orthogonal componentsquare calculation unit that receives the base band signal, calculatessquare of an orthogonal component of the base band signal and outputsthe squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; an adder that adds the signedsquared in-phase and orthogonal components, generates a squared additionsignal using a result of this addition, and outputs this signal; asubtracter that subtracts the signed squared in-phase component from thesigned squared orthogonal component or vice versa, and generates andoutputs a squared subtraction signal using a result of this subtraction;a squared-addition signal component correlation calculating unit thatcalculates correlation value between the squared addition signal and a ½symbol frequency component, and outputs this correlation value as anaddition correlation signal; a squared-subtraction signal componentcorrelation calculating unit that calculates correlation value betweenthe squared subtraction signal and the ½ symbol frequency component, andoutputs this correlation value as a subtraction correlation signal; avector selecting unit that compares the magnitude of the additioncorrelation signal with the magnitude of the subtraction correlationsignal, selects the addition correlation signal or the subtractioncorrelation signal whichever is larger, and outputs this signal as aselected correlation signal; and a timing phase difference calculatingunit that outputs a phase control signal from a vector angle shown bythe selected correlation signal.

Further, the timing regenerating device according to still anotheraspect of the invention comprises an in-phase component squarecalculation unit that receives a base band signal having a preamblesymbol, calculates square of an in-phase component of the base bandsignal and outputs the squared in-phase component; an in-phasemultiplier that multiplies a sign bit (±1) of the in-phase component ofthe base band signal to the squared in-phase component and outputs theresult as signed squared in-phase component; an orthogonal componentsquare calculation unit that receives the base band signal, calculatessquare of an orthogonal component of the base band signal and outputsthe squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; an adder that adds the signedsquared in-phase and orthogonal components, generates a squared additionsignal using a result of this addition, and outputs this signal; asubtracter that subtracts the signed squared in-phase component from thesigned squared orthogonal component or vice versa, and generates andoutputs a squared subtraction signal using a result of this subtraction;a squared-addition signal component correlation calculating unit thatcalculates correlation value between the squared addition signal and a ½symbol frequency component, and outputs this correlation value as anaddition correlation signal; a squared-subtraction signal componentcorrelation calculating unit that calculates correlation value betweenthe squared subtraction signal and the ½ symbol frequency component, andoutputs this correlation value as a subtraction correlation signal; avector selecting unit that compares the magnitude of the additioncorrelation signal with the magnitude of the subtraction correlationsignal, selects the addition correlation signal or the subtractioncorrelation signal whichever is larger, and outputs this signal as aselected correlation signal; and a preamble detecting/timing phasedifference calculating unit that calculates a vector angle and a vectorlength of the selected correlation signal, decides that the preamblesymbol has been detected when the vector length is larger than apredetermined threshold value, calculates a timing phase differenceusing a vector angle shown by the selected correlation signal at thattime, and outputs a phase control signal.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises a VCO thatoutputs a regeneration symbol clock, a regeneration sample clock, and a½ symbol frequency component, based on a phase control signal. The baseband signal to be input into the in-phase component square calculationunit and the orthogonal component square calculation unit is a signalthat has been sampled based on the regeneration sample clock. Thesquared-addition signal component correlation calculating unitcalculates correlation value using the ½ symbol frequency componentoutput from the VCO, and the squared-subtraction signal componentcorrelation calculating unit calculates correlation value using the ½symbol frequency component output from the VCO.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises a phasedetecting unit that detects advancement/delay of a timing phase usingthe base band signal sampled based on the regeneration sample clock, andoutputs detected signals as phase detection signals; and a phasedetection signal averaging unit that calculates an average of the phasedetection signals, and outputs the average as a phase advance/delaysignal, wherein the VCO outputs a regeneration symbol clock, aregeneration sample clock, and a ½ symbol frequency component, based onboth the phase control signal and the phase advance/delay signal.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises an oscillatorthat outputs an asynchronous sample clock and a ½ symbol frequencycomponent. The base band signal to be input into the in-phase componentsquare calculation unit and the orthogonal component square calculationunit is a signal that has been sampled by the asynchronous sample clock.The squared-addition signal component correlation calculating unitcalculates correlation value using the ½ symbol frequency componentoutput from the oscillator. The squared-subtraction signal componentcorrelation calculating unit calculates correlation value using the ½symbol frequency component output from the oscillator.

Further, the timing regenerating device according to still anotheraspect of the invention comprises an in-phase component squarecalculation unit that receives a base band signal having a preamblesymbol, calculates square of an in-phase component of the base bandsignal and outputs the squared in-phase component; an in-phasemultiplier that multiplies a sign bit (±1) of the in-phase component ofthe base band signal to the squared in-phase component and outputs theresult as signed squared in-phase component; an orthogonal componentsquare calculation unit that receives the base band signal, calculatessquare of an orthogonal component of the base band signal and outputsthe squared orthogonal component; orthogonal multiplier that multipliesa sign bit (±1) of the orthogonal component of the base band signal tothe squared orthogonal component and outputs the result as a signedsquared orthogonal component; an adder that adds the signed squaredin-phase and orthogonal components, generates a squared addition signalusing a result of this addition, and outputs this signal; a subtracterthat subtracts the signed squared in-phase component from the signedsquared orthogonal component or vice versa, and generates and outputs asquared subtraction signal using a result of this subtraction; asquared-addition signal component correlation calculating unit thatcalculates correlation value between the squared addition signal and a ½symbol frequency component, and outputs this correlation value as anaddition correlation signal; a squared-subtraction signal componentcorrelation calculating unit that calculates correlation value betweenthe squared subtraction signal and the ½ symbol frequency component, andoutputs this correlation value as a subtraction correlation signal; avector selecting unit that compares the magnitude of the additioncorrelation signal with the magnitude of the subtraction correlationsignal, selects the addition correlation signal or the subtractioncorrelation signal whichever is larger, and outputs this signal as aselected correlation signal; a weighting unit that gives a weightcorresponding to a magnitude of a vector length shown by the selectedcorrelation signal to the selected correlation signal, and outputs theweighted selected correlation signal as a weighted correlation signal;an averaging unit that multiplies the weighted correlation signal bytwo, calculates an average of the signal, and outputs this average as aweighted average correlation signal; and a timing phase differencecalculating unit that outputs a phase control signal from a vector angleshown by the weighted average correlation signal.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises a VCO thatoutputs a regeneration symbol clock, a regeneration sample clock, and a½ symbol frequency component, based on a phase control signal. The baseband signal to be input into the in-phase component square calculationunit and the orthogonal component square calculation unit is a signalthat has been sampled based on the regeneration sample clock. Thesquared-addition signal component correlation calculating unitcalculates correlation value using the ½ symbol frequency componentoutput from the VCO, and the squared-subtraction signal componentcorrelation calculating unit calculates correlation value using the ½symbol frequency component output from the VCO.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises an oscillatorthat outputs an asynchronous sample clock and a ½ symbol frequencycomponent. The base band signal to be input into the in-phase componentsquare calculation unit and the orthogonal component square calculationunit is a signal that has been sampled by the asynchronous sample clock.The squared-addition signal component correlation calculating unitcalculates correlation value using the ½ symbol frequency componentoutput from the oscillator, and the squared-subtraction signal componentcorrelation calculating unit calculates correlation value using the ½symbol frequency component output from the oscillator.

Further, according to still another aspect of the invention, in thetiming regenerating device of the above aspect, the adder adds a signedsquared in-phase and orthogonal components to obtain a result as asquared addition signal, and the subtracter subtracts the signed squaredin-phase component from the signed squared orthogonal component or viceversa, and obtains a result as a squared subtraction signal.

Further, according to still another aspect of the invention, in thetiming regenerating device of the above aspect, the adder adds a signedsquared in-phase and orthogonal components, and obtains a square root ofthis sum as a squared addition signal, and the subtracter subtracts thesigned squared in-phase component from the signed squared orthogonalcomponent or vice versa, and obtains a square root of this difference asa squared subtraction signal.

Further, according to still another aspect of the invention, in thetiming regenerating device of the above aspect, when the in-phasecomponent of a weighted correlation signal is negative, the averagingunit inverts the signs of the in-phase and orthogonal components of theweighted correlation signal respectively, and generates a correlationsignal with the inverted signs as a first correlation signal. On theother hand, when the in-phase component of the weighted correlationsignal is positive, the averaging unit generates this weightedcorrelation signal as a first correlation signal. Furthermore, when theorthogonal component of the weighted correlation signal is negative, theaveraging unit inverts the signs of the in-phase and orthogonalcomponents of the weighted correlation signal respectively, andgenerates a correlation signal with the inverted signs as a secondcorrelation signal. On the other hand, when the orthogonal component ofthe weighted correlation signal is positive, the averaging unitgenerates this weighted correlation signal as a second correlationsignal, and the averaging unit calculates an average of the first andsecond correlation signals respectively. Furthermore, when the vectorlength of the averaged first correlation signal is larger than thevector length of the averaged second correlation signal, the averagingunit outputs the averaged first correlation signal as the weightedaverage correlation signal. On the other hand, when the vector length ofthe averaged second correlation signal is larger than the vector lengthof the averaged first correlation signal, the averaging unit outputs theaveraged second correlation signal as the weighted average correlationsignal.

Further, according to still another aspect of the invention, the timingregenerating device of the above aspect further comprises a clipdetecting unit that receives a base band signal having a preamblesymbol, converts both the in-phase and orthogonal components of the baseband signal into “0” when at least one value of in-phase and orthogonalcomponents of the base band signal is outside a predetermined range, andoutputs the base band signal straight when at least one value ofin-phase and orthogonal components of the base band signal is within thepredetermined range. The base band signal input into the in-phasecomponent square calculation unit and the orthogonal component squarecalculation unit is the base band signal output from the clip detectingunit.

Further, the demodulator according to still another aspect of theinvention comprises an antenna that receives a radio signal; a frequencyconverting unit that converts the frequency of the received radio signalinto the frequency of a base band signal; an A/D converting unit thatconverts the base band signal into a digital base band signal based on asampling at two times a symbol rate using a regeneration sample clock; atiming regenerating device; and a data deciding unit that extractsNyquist point data from the digital base band signal using theregeneration symbol clock, decides the extracted Nyquist point data, andoutputs the data as demodulated data.

Further, the demodulator according to still another aspect of theinvention comprises an antenna that receives a radio signal; a frequencyconverting unit that converts the frequency of the received radio signalinto the frequency of a base band signal; an A/D converting unit thatconverts the base band signal into a digital base band signal based on asampling at two times a symbol rate using the asynchronous sample clock;a timing regenerating device; a data interpolating unit thatinterpolates the digital base band signal that has been sampled by theasynchronous sample clock, and outputs the interpolated data as aninterpolated base band signal; and a data deciding unit that extracts aNyquist point of the interpolated base band signal based on a phasecontrol signal, decides data at the extracted Nyquist point, and outputsthe data as demodulated data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structure diagram of a demodulator according to a firstembodiment of the present invention;

FIG. 2 is a diagram showing a sampling status of a preamble symbol;

FIG. 3 is a diagram showing a sampling status of a preamble symbol;

FIG. 4 is a diagram showing combined correlation values (ΣC, ΣS);

FIG. 5 is a diagram showing the operation of preamble detecting/timingphase difference calculating unit;

FIG. 6 is a structure diagram of a demodulator according to a secondembodiment of the present invention;

FIG. 7 is structure diagram of a demodulator according to a thirdembodiment of the present invention;

FIG. 8 is a structure diagram of a demodulator according to a fourthembodiment of the present invention;

FIG. 9 is a structure diagram of vector selecting unit according to thefourth embodiment of the present invention;

FIG. 10 is a diagram showing a sampling status of a preamble symbol;

FIG. 11 is a diagram showing a sampling status of a preamble symbol;

FIG. 12 is a diagram showing addition correlation signals (CA_(i),SA_(i)) and subtraction correlation signals (CS_(i), SS_(i));

FIG. 13 is a diagram showing addition correlation signals (CA_(i),SA_(i)) and subtraction correlation signals (CS_(i), SS_(i));

FIG. 14 is a structure diagram of a demodulator according to a fifthembodiment of the present invention;

FIG. 15 is a structure diagram of a demodulator according to a sixthembodiment of the present invention;

FIG. 16 is a structure diagram of a demodulator according to a seventhembodiment of the present invention;

FIG. 17 is a structure diagram of a demodulator according to an eighthembodiment of the present invention;

FIG. 18 is a structure diagram of vector selecting unit according to aninth embodiment of the present invention;

FIG. 19 is a structure diagram of a demodulator according to a tenthembodiment of the present invention;

FIG. 20 is a structure diagram of a conventional demodulator;

FIG. 21 is a structure diagram of vector combination selecting unit;

FIG. 22 is a signal space diagram showing a preamble symbol (“1001”pattern);

FIG. 23 is a diagram showing a sampling status of a preamble symbol;

FIG. 24 is a diagram showing correlation values (CI, SI) and correlationvalues (CQ, SQ);

FIG. 25 is a signal space diagram showing a preamble symbol (“1001”pattern);

FIG. 26 is a diagram showing a sampling status of a preamble symbol;

FIG. 27 is a diagram showing correlation values (CI, SI) and correlationvalues (CQ, SQ);

FIG. 28 is a diagram showing combined correlation values (ΣC, ΣS);

FIG. 29 is a diagram showing combined correlation values (ΣC, ΣS);

FIG. 30 is a structure diagram of vector combination selecting unit;

FIG. 31 is a preamble symbol space diagram when a carrier phase θc is 45[deg];

FIG. 32 is a diagram showing a sampling status of a preamble symbol;

FIG. 33 is a diagram showing combined correlation values (ΣC, ΣS);

FIG. 34 is a preamble symbol space diagram when a carrier phase θc is 90[deg];

FIG. 35 is a diagram showing a sampling status of a preamble symbol; and

FIG. 36 is a signal space diagram showing a preamble symbol (“1101”pattern).

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a structure diagram of a demodulator according to a firstembodiment of the present invention. Sections identical to orcorresponding to those of the conventional demodulator shown in FIG. 20are attached with the same reference numbers.

This demodulator mainly comprises antenna 100, frequency converting unit200, first A/D converter 301 a, second A/D converter 301 b, timingregenerating device 400, and data deciding unit 500. The timingregenerating device 400 mainly comprises VCO 401, in-phase componentsquare calculation unit 420 a, orthogonal component square calculationunit 420 b, in-phase multiplier 421 a, orthogonal multiplier 421 b,squared-preamble in-phase correlation calculating unit 422 a,squared-preamble orthogonal correlation calculating unit 422 b, vectorcombination selecting unit 405, and preamble detecting/timing phasedifference calculating unit 423.

Detail operation of the demodulator will be explained next. First, theantenna 100 receives a burst signal of RF band. The frequency convertingunit 200 frequency converts the burst signal of the RF band into a burstsignal of a base band. This burst signal has a preamble symbol at theheader. Significant data exists after the preamble symbol. The preamblesymbol used here may be a signal (for example; the “1001” pattern) asshown in FIG. 22 or a signal (for example, the “1101” pattern) as shownin FIG. 36.

The first A/D converter 301 a samples the in-phase component of thereceived signal of the base band at time t=τ+iT/2 (where i=1, 2, 3, . .. , and τ represents a timing error (−T/2≦τ<T/2), and T represents asymbol frequency), and outputs a received data string I_(i) (i=1, 2, 3,. . . ) as the in-phase component of the received signal.

Similarly, the second A/D converter 301 b samples the orthogonalcomponent of the received signal of the base band at time t=τ+iT/2, andoutputs a received data string Q_(i) (i=1, 2, 3, . . . ) as theorthogonal component of the received signal. The A/D converters 301 aand 301 b sample the data using the regeneration sample clock outputfrom the timing regenerating device 400 respectively.

According to the conventional first A/D converter 300 a and second A/Dconverter 300 b, the data to be sampled is limited to the preamble.However, the first A/D converter 301 a and the second A/D converter 301b are different from these conventional converters in that the first A/Dconverter 301 a and the second A/D converter 301 b sample all thereceived strings including significant data in addition to the preamble.

The timing regenerating device 400 detects the preamble symbols (Ip_(i),Qp_(i)) within the burst signal using the received data string I_(i)(i=1, 2, 3, . . . ) and the received data string Q_(i) (i=1, 2, 3, . . .), calculates a timing error τ using the preamble symbols, and carriesout a phase control for controlling the timing error τ to a regenerationsample clock and a regeneration symbol clock. The regeneration symbolclock is a clock of a symbol period having the regeneration sample clockfrequency-divided into two.

The data deciding unit 500 receives significant random data strings Idiand Qdi (i=1, 2, 3, . . . ) that follow the preambles after the timingerror τ has been cancelled by the timing regenerating device 400, andlatches the data at the Nyquist points by the regeneration symbol clock.Then, the data deciding unit 500 decides the data using the latchedNyquist point data, and outputs the demodulated data.

Detail operation of the timing regenerating device 400 will be explainedbelow.

First, the in-phase component square calculation unit 420 a calculates asquare of the in-phase component I_(i) of the received signal, and theorthogonal component square calculation unit 420 b calculates a squareof the orthogonal component Q_(i) of the received signal.

The in-phase multiplier 421 a multiplies a sign I_(i) shown by theequations (17a) and (17b) of the in-phase component I_(i) of thereceived signal to |I_(i)|² output from the in-phase component squarecalculation unit 420 a:

sign I _(i)=+1(I _(i)≧0)  (17a)

 sign I _(i)=−1(I _(i)<0)  (17b)

Then, the in-phase multiplier 421 a outputs a signed squared in-phasecomponent DI_(i) as follows:

DI _(i)=sign I _(i) ×|I _(i)|²  (18a)

Similarly, the orthogonal multiplier 421 b multiplies a sign Q_(i) shownby the equations (17c) and (17d) of the orthogonal component Q_(i) ofthe received signal to |Q_(i)|² output from the orthogonal componentsquare calculation unit 420 b:

sign Q _(i)=+1(Q _(i)≧0)  (17c)

sign Q _(i)=−1(Q _(i)<0)  (17d)

Then, the orthogonal multiplier 421 b outputs a signed squaredorthogonal component DQ_(i) as follows:

DQ _(i)=sign Q _(i) ×|Q _(i)|²  (18b)

The squared-preamble in-phase correlation calculating unit 422 areceives the signed squared in-phase component DI_(i) (i=1, 2, 3, . . .), and carries out the multiplication of a ½ symbol frequency componentbased on the equations (19a) and (19b):

DIc _(i) =DI _(i)×cos πi/2  (19a)

DIs _(i) =DI _(i)×sin πi/2  (19b)

Then, the squared-preamble in-phase correlation calculating unit 422 acalculates an average of the results of the multiplication (DIc_(i),DIs_(i)), obtains correlation values (CI_(i), SI_(i)), and outputs themas in-phase correlation signals.

Similarly, the squared-preamble orthogonal correlation calculating unit422 b carries out the multiplication of a ½ symbol frequency componentto the signed squared orthogonal component DQ_(i) (i=1, 2, 3, . . . )based on the equations (20a) and (20b):

DQc _(i) =DQ _(i)×cos πi/2  (20a)

DQs _(i) =DQ _(i)×sin πi/2  (20b)

Then, the squared-preamble orthogonal correlation calculating unit 422 bcalculates an average of the results of the multiplication (DQc_(i),DQs_(i)), obtains correlation values (CQ_(i), SQ_(i)), and outputs themas orthogonal correlation signals.

The multiplication in the equations (19a), (19b), (20a) and (20b) issimple as cos πi/2=1, 0, −1, 0, . . . , and sin πi/2=0, 1, 0, −1, . . ., and the correlation values (CI_(i), SI_(i)) and (CQ_(i), SQ_(i)) canbe obtained easily, in a similar manner to that of the multiplication ofthe equations (1a), (1b), (2a) and (2b).

The vector combination selecting unit 405 receives the correlationvalues (CI_(i), CQ_(i)) and the correlation values (SI_(i), SQ_(i)),combines and selects based on the processing similar to the conventionalprocessing, and outputs the combined correlation signals (ΣC_(i),ΣS_(i)). Based on this, it is possible to remove the influence of thecarrier phase θc.

When “E” represents an envelope level, when receiving a preamble symbolthat repeats ±180 [deg] for each one symbol as shown in FIG. 22, theamplitude of the signed squared in-phase component becomes (E cos θc)²,and the amplitude of the signed squared orthogonal component becomes (Esin θc)². The sum of these amplitudes becomes constant as (E cos θc)²+(Esin θc)²=E² regardless of the carrier phase θc. Similarly, the combinedcorrelation signals (ΣC_(i), ΣS_(i)) that are the sums of the magnitudesof the correlation values (CI_(i), SI_(i)) obtained from the signedsquared in-phase component and the magnitudes of the correlation values(CQ_(i), SQ_(i)) obtained from the signed squared orthogonal componentbecome constant regardless of the carrier phase θc.

How the combined correlation signals (ΣC_(i), ΣS_(i)) will arecalculated will be explained here taking into consideration cases wherethe carrier phase θc is 45 [deg] and 90 [deg].

When the preamble symbol having the carrier phase θc=45 [deg] as shownin FIG. 31 is received at the timings of the vertical lines shown inFIG. 32, the amplitude of the signed squared in-phase component and theamplitude of the signed squared orthogonal component become A²/2. On theother hand, when the preamble symbol having the carrier phase θc=90[deg] as shown in FIG. 34 is received at the same timings as the timingsin FIG. 32, that is, at the timings of the vertical lines shown in FIG.35, the signed squared in-phase component becomes “0”, and the signedsquared orthogonal component becomes A².

Therefore, the sum (A²/2+A²/2) of the amplitudes of the signed squaredin-phase and orthogonal components when the carrier phase θc=45 [deg]becomes equal to the sum (0+A²) of the amplitude of the signed squaredin-phase and orthogonal components when the carrier phase θc=90 [deg].Similarly, the combined correlation signals (ΣC_(i), ΣS_(i)) when thecarrier phase θc=45 [deg] and the combined correlation signals (ΣC_(i),ΣS_(i)) when the carrier phase θc=90 [deg] coincide with each other asshown in FIG. 4. According to the conventional example, the combinedcorrelation signals when the carrier phase θc=45 [deg] become largerthan the combined correlation signals when the carrier phase θc=90[deg]. Thus, the magnitude of the combined correlation signals (ΣC_(i),ΣS_(i)) varies depending on the carrier phase θc. However, it can beobserved that, according to the present embodiment, the magnitude of thecombined correlation signals (ΣC_(i), ΣS_(i)) becomes constantregardless of the carrier phase (that is, both when the carrier phase θcis 45 and when it is 90 [deg]).

The preamble detecting/timing phase difference calculating unit 423carries out the processing of obtaining a vector length V_(i) of thecombined correlation signals (ΣC_(i), ΣS_(i)) and also the processing ofobtaining a vector angle θo_(i).

The vector length V_(i) is obtained based on the equation (21):

Vi=(|ΣC _(i)|² +|ΣS _(i)|²)^(1/2)  (21)

The vector angle θo_(i) is obtained based on the equation (22):

θO _(i)=tan⁻¹(ΣS _(i) /ΣC _(i))  (22)

θo_(i) is a timing phase difference when the normalization has beencarried out in the 2 symbol period (2T), like θ_(T). Therefore, a timingphase difference θr_(i) [deg] when the normalization has been carriedout in the symbol period (T) is obtained using the equation (23):

θr _(i)=2θo _(i) mod 360  (23)

The processing of the equation (22) may be carried out based on thevalues (sign [ΣC_(i)]*|ΣC_(i)|^(1/2), sign [ΣS_(i)]*|ΣS_(i)|^(1/2))obtained by multiplying the sign {±1} of each correlation signal to thesquare root of each absolute value of the combined correlation signals(ΣC_(i), ΣS_(i)). In this case, the vector angle θo_(i) is obtainedusing the following equation:

θo _(i)=tan⁻¹(sign [ΣS _(i) ]·|S _(i)|Σ^(1/2)/sign [ΣC _(i) ]·|ΣC_(i)|^(1/2))  (22a)

The calculations in the equation 22a are more complex than those of theequation (22). However, it is possible to calculate the timing phasedifference in higher precision.

When the timing regenerating device 400 is receiving a preamble symbolas shown in FIG. 22, for example, the vector length V_(i) becomeslarger, and the timing phase difference θr_(i) [deg] becomes a certainvalue. On the other hand, when the timing regenerating device 400 isreceiving no signal (receiving only noise in the absence of a signal) orwhen the timing regenerating device 400 is receiving a significant datasection that follows the preamble, the vector length V_(i) becomessmaller, and the timing phase difference θr_(i) [deg] becomes anuncertain value. FIG. 5 shows a relationship between V_(i) and the levelof certainty of θr_(i) according to the reception status.

Therefore, even if the reception timing of the burst signal and thearrival time of the preamble symbol is not known, it becomes possible toobtain the timing error τ based on the following processing.

When a vector length V_(i) is large as a result of monitoring V_(i) (forexample, when the vector length V_(i) exceeds a certain threshold valueεp), a decision is made that “preamble is being received”, and thetiming phase difference θr_(i) [deg] is latched at the timing shown inFIG. 5. As is clear from FIG. 5, the latched timing phase differenceθr_(i) [deg] is a timing phase difference θr_(i) [deg] when V_(i) islarge. Therefore, this is a certain value. The preamble detecting/timingphase difference calculating unit 423 obtains the timing error τ fromthe equations (16a) and (16b) using the timing phase difference θsobtained as described above, and gives a phase control signal forcanceling the timing error τ to the VCO 401 at the latter stage.

Assume, for example, that the detection of the preamble is carried outin a similar manner using the preamble detecting/timing phase differencecalculating unit 423 in place of the conventional timing phasedifference calculating unit 402. In this case, the magnitude (=vectorlength V_(i)) of the combined correlation signals (ΣC, ΣS) changesdepending on the carrier phase θc. Therefore, the preamble detectioncharacteristics for detecting the vector length V_(i) based on thethreshold value εp are influenced by the carrier phase θc. However,according to the present embodiment, the magnitude (=vector lengthV_(i)) of the combined correlation signals (ΣC_(i), ΣS_(i)) is constantregardless of the carrier phase θc. Therefore, the preamble detectioncharacteristics for detecting the vector length V_(i) based on thethreshold value εp are not influenced by the carrier phase θc.

When the reception timing of the burst signal is known and also when thearrival time of the preamble can be specified, the preamble detectionoperation is not necessary. Therefore, in this case, it is of coursepossible to use the conventional timing phase difference calculatingunit 402 in place of the preamble detecting/timing phase differencecalculating unit 423. Since the function of obtaining the vector lengthV_(i) and detecting its magnitude is not necessary, it is possible toreduce the circuit scale.

The VCO 401 receives the phase control signal from the preambledetecting/timing phase difference calculating unit 423, controls thephases of the regeneration sample clock and the regeneration symbolclock, and sets the timing error τ to “0”. Further, the VCO 401 outputsthe regeneration sample clock. This regeneration sample clock is used bythe first A/D converting unit 301 a and the first A/D converting unit301 b for sampling the base band signal. Further, the VCO 401 outputs a½ symbol frequency component. This ½ symbol frequency component is usedby the squared-preamble in-phase correlation calculating unit 422 a andthe squared-preamble orthogonal correlation calculating unit 522 brespectively for calculating correlation values.

As explained above, a correlation calculation with the preamble symbolhaving a ½ symbol frequency component is carried out using a signalobtained by multiplying the sign bit (±1) of the in-phase component ofthe preamble symbol to the squared value of the in-phase component and asignal obtained by multiplying the sign bit (±1) of the orthogonalcomponent of the preamble symbol to the squared value of the orthogonalcomponent. Therefore, it is possible to realize the estimation of atiming phase at high precision without the influence of the carrierphase θc.

Further, the preamble detecting/timing phase difference calculating unit423 can simultaneously realize the estimation of a timing phase at highprecision using a preamble and the detection of a preamble. Therefore,it is possible to carry out the timing phase control normally even whenthe reception timing of the preamble is not known. In this case, thepreamble detection characteristics are not influenced by the carrierphase θc. Further, it is possible to realize the above at a low samplingspeed of 2 [sample/symbol].

Further, it is possible to realize a high-speed synchronization and ahigh-speed resynchronization in a short preamble without receiving aninfluence of a carrier phase θc, and to realize a satisfactory BER(bit-error ratio) characteristics in a significant data section thatfollows the preamble, even when the reception timing of a burst signalthat occurs at the power supply start-up time or at the reconnectiontiming after a recovery from a shadowing is unknown.

Further, the timing regenerating device 400 can carry out the estimationof a timing phase and the detection of a preamble at high precisionregardless of a carrier phase, when the preamble symbol is a signal thatalternately shifts between two points for each one symbol on a complexplane, like the preamble symbol that alternately shifts between twoadjacent Nyquist points for each symbol on the complex plane as shown inFIG. 36, in addition to the preamble symbol that alternately shiftsbetween two Nyquist points for each symbol that become symmetrical withthe origin (that shifts ±180 [deg] for each symbol) on the complex planeas shown in FIG. 22.

FIG. 6 is a structure diagram of a demodulator according to a secondembodiment of the present invention. This demodulator has a feedbacksystem circuit called a PLL (Phase Lock Loop) built into the demodulatorshown in FIG. 1. Sections identical to or corresponding to the portionsof the demodulator shown in FIG. 1 are attached with the same referencenumbers.

This demodulator comprises a PLL timing regenerating unit that includesphase detecting unit 424, averaging unit 425, and VCO 401 a. This PLLtiming regenerating unit is described in, for example, the document“Timing Recovery Scheme Using Received Signal Phase Information for QPSKModulation” (by Fujimura, in Proceedings of Electronic InformationCommunication Association, Vol. J81-B-II No. 6, pp. 665-668, June,1998).

The operation of the demodulator will be explained now. First, in thesame manner as in the first embodiment, the PLL timing regenerating unitconsisting of the phase detecting unit 417, the averaging unit 418, andthe VCO 401 a is operated at the time of detecting a preamble or at thetime of calculating a timing error τ.

In this case, the processing performed by the in-phase component squarecalculation unit 420 a, orthogonal component square calculation unit 420b, vector combination selecting unit 405, and preamble detecting/timingphase difference calculating unit 423 is similar to that of the firstembodiment. That is, when a preamble symbol has been detected, a clockphase control for canceling the timing error τ obtained at the same timeas this detection is given to the VCO 401 a as a phase control signal.

In the mean time, the phase detecting unit 424 detects whether a timingphase is advanced or delayed from received data (I_(i), Q_(i)). When thetiming phase is advanced as a detection signal, “+1” is output, and whenthe timing phase is delayed, “−1” is output. The averaging unit 425receives this advance/delay signal, calculates an average of the signalsusing a random work filter, for example, and outputs the value as aphase advance/delay signal.

The VCO 401 a receives this phase advance/delay signal, and controls thephases of a regeneration sample clock and a regeneration symbol clock.When this phase advance/delay signal is “positive”, the VCO 401 aadvances the timing phase, and when the phase advance/delay signal is“negative”, the VCO 401 a delays the timing phase. The VCO 401 a isusually controlled based on the phase advance/delay signal. However,when a preamble has been detected and also when a phase control signalhas been input, the VCO 401 a controls each clock phase by using thephase control signal without using the phase advance/delay signal.

When only the phase advance/delay signal is used, this has adisadvantage that it takes time to lead the timing phase, as theadvancement/delay control of the timing phase using this phaseadvance/delay signal is carried out in the {fraction (1/16)} symbol stepwidth, for example. On the other hand, this has an advantage that it ispossible to trace the timing phase during the reception of a significantrandom data section that follows the preamble symbol.

In the mean time, when only the phase control signal is used, this has adisadvantage that a timing phase difference θr_(i) [deg] becomesuncertain and cannot be used during the reception of a significantrandom data section that follows the preamble symbol. On the other hand,this has an advantage that it is possible to detect a timing phasedifference at high precision based on a short preamble symbol.

Since both the phase control signal and the phase advance/delay signalare used, the advantages cover the disadvantages. Therefore, it ispossible to realize the tracing of the timing phase during the receptionof the significant random data while carrying out the estimating andcontrol of the timing phase at high precision using a short preamblesymbol.

Further, like in the first embodiment, the timing regenerating device400 can carry out the estimation of a timing phase and the detection ofa preamble at high precision regardless of a carrier phase, when thepreamble symbol is a signal that alternately shifts between two pointsfor each one symbol on a complex plane, like the preamble symbol thatalternately shifts between two adjacent Nyquist points for each symbolon the complex plane as shown in FIG. 36, in addition to the preamblesymbol that alternately shifts between two Nyquist points for eachsymbol that become symmetrical with the origin (that shifts ±180 [deg]for each symbol) on the complex plane as shown in FIG. 22.

FIG. 7 is a structure diagram of a demodulator according to a thirdembodiment of the present invention. A feed forward type timingregenerating device is used in place of the VCO 401 in the demodulatorshown in FIG. 1. Sections identical to or corresponding to the portionsof the demodulator shown in FIG. 1 are attached with the same referencenumbers.

The demodulator also comprises oscillator 426, data interpolating unit600, and data deciding unit 500 a.

Operation of the demodulator according to the third embodiment will nowbe explained will now be explained. The oscillator 426 outputs anasynchronous sample clock that self-runs at two times the symbol period.The first A/D converter 301 a and second A/D converter 301 basynchronously sample the data at 2 [sample/symbol] by this asynchronoussample clock.

The in-phase component square calculation unit 420 a and orthogonalcomponent square calculation unit 420 b obtain the square of theasynchronously sampled received data (I_(i), Q_(i)) The in-phasemultiplier 421 a and orthogonal multiplier 421 b multiply the sign (±1)of the received data (I_(i), Q_(i)) to the input squared values obtainedby the in-phase component square calculation unit 420 a and theorthogonal component square calculation unit 420 b respectively. Thesquared-preamble in-phase correlation calculating unit 422 a calculatescorrelation between the signal DI_(i) output from the in-phasemultiplier 421 a and a ½ frequency component exp[−jπ(fs)t] of the symbolfrequency output from the oscillator 426. The squared-preambleorthogonal correlation calculating unit 422 b calculates correlationbetween the signal DQ_(i) output from the orthogonal multiplier 421 band a ½ frequency component exp[−jπ(fs)t] of the symbol frequency outputfrom the oscillator 426. Thereafter, vector combination selecting unit405 and preamble detecting/timing phase difference calculating unit 423obtain the timing error τ.

The data interpolating unit 600 interpolates the data (I_(i), Q_(i))received by the first A/D converter 301 a and the second A/D converter301 b, generates a received data having a time resolution of {fraction(1/16)} of the symbol period, for example, and outputs the interpolatedreceived data.

The data deciding unit 500 a extracts a Nyquist point of theinterpolated received data using the information of the timing error τfrom the preamble detecting/timing phase difference calculating unit423, and outputs the data of the extracted Nyquist point as demodulateddata.

As explained above, based on the use of the low-cost and compactoscillator 426 in place of the VCO having a large circuit scale, it ispossible to make the demodulator compact at low cost.

Further, like in the first embodiment, the timing regenerating device400 can carry out the estimation of the timing phase and the detectionof the preamble at high precision regardless of a carrier phase, whenthe preamble symbol is a signal that alternately shifts between twopoints for each one symbol on a complex plane, like the preamble symbolthat alternately shifts between two adjacent Nyquist points for eachsymbol on the complex plane as shown in FIG. 36, in addition to thepreamble symbol that alternately shifts between two Nyquist points foreach symbol that become symmetrical with the origin (that shifts ±180[deg] for each symbol) on the complex plane as shown in FIG. 22.

FIG. 8 is a structure diagramof ademodulator according to a fourthembodiment of the present invention. Sections identical to orcorresponding to the portions of the demodulator shown in FIG. 1 areattached with the same reference numbers. In FIG. 8, 423 a denotespreamble detecting/timing phase difference calculating unit, 427 denotesadder, 428 denotes subtracter, 429 a denotes squared-addition signalcomponent correlation calculating unit, 429 b denotessquared-subtraction signal component correlation calculating unit, and430 denotes vector selecting unit.

Detail structure of the vector selecting unit 430 is shown in FIG. 9.This selecting unit 430 comprises maximum absolute value detecting unit431, and selecting unit 432.

Operation of the demodulator according to the fourth embodiment will nowbe explained. The adder 427 adds a signed squared in-phase componentDI_(i) output from the in-phase multiplier 421 a and a signed squaredorthogonal component DQ_(i) output from the orthogonal multiplier 421 b,and outputs a result as a squared addition signal A_(i). On the otherhand, the subtracter 428 subtracts the signed squared in-phase componentDI_(i) output from the in-phase multiplier 421 a from the signed squaredorthogonal component DQ_(i) output from the orthogonal multiplier 421 b,and outputs a result as a squared subtraction signal S_(i). Thesubtraction performed by the subtracter 428 may be either(DI_(i)−DQ_(i)) or (DQ_(i)−DI_(i)).

When a preamble symbol has been received (I_(i)=Ip_(i), Q_(i)=Qp_(i)),regardless of the value of the carrier phase θc [deg], either one of thesquared addition signal output from the adder 427 and the squaredsubtraction signal output from the subtracter 428 can become a signalhaving a large ½ symbol frequency component. For example, when thecarrier phase θc [deg] is within the range of (90<θc<180) or(270<θc<360) as shown in FIG. 22, the phases of the in-phase andorthogonal components of the preamble symbol becomes in the oppositephase relationship as shown in FIG. 23. Therefore, the signed squaredin-phase component DI_(i) and the signed squared orthogonal componentDQ_(i) obtained by multiplying the sign (±1) to these squared valuesrespectively also become in the opposite phase relationship.

Therefore, the amplitude of the squared addition signal A_(i) becomessmall as shown in FIG. 10(a) based on the cancellation of both signals.On the other hand, the amplitude of the squared subtraction signal S_(i)becomes large as shown in FIG. 10(b) based on the in-phase relationshipbetween the signed squared in-phase component DI_(i) and the invertedsigned squared orthogonal component DQ_(i).

When the carrier phase θc [deg] is within the range of (90<θc<180) or(270<θc<360) as shown in FIG. 22, the absolute value of the amplitude ofthe squared subtraction signal S_(i) becomes ||I_(i)|²+|Q_(i)|²|, whichis constant (the squared value of the envelope E: E²) regardless of thecarrier phase θc. (The absolute value of the squared addition signalA_(i) becomes ||I_(i)|²−|Q_(i)|²|, and this changes depending on thecarrier phase θc.)

On the other hand, when the carrier phase θc [deg] is within the rangeof (0<θc<90) or (180<θc<270) as shown in FIG. 25, the phases of thein-phase and orthogonal components of the preamble symbol are in-phaseas shown in FIG. 26. Therefore, the signed squared in-phase componentDI_(i) and the signed squared orthogonal component DQ_(i) obtained bymultiplying the sign (±1) to these squared values respectively alsobecome in the in-phase phase relationship. Therefore, the amplitude ofthe squared addition signal A_(i) becomes large as shown in FIG. 11(a).On the other hand, the amplitude of the squared subtraction signal S_(i)becomes small as shown in FIG. 11(b) based on the opposite-phaserelationship between the signed squared in-phase component DI_(i) andthe inverted signed squared orthogonal component DQ_(i).

Similarly, when the carrier phase θc [deg] is within the range of(0<θc<90) or (180<θc<270) as shown in FIG. 25, the absolute value of theamplitude of the squared addition signal A_(i) becomes||I_(i)|²+|Q_(i)|²|, which is constant (the squared value of theenvelope E: E²) regardless of the carrier phase θc. (The absolute valueof the squared subtraction signal S_(i) becomes ||I_(i)|²−|Q_(i)|²|, andthis changes depending on the carrier phase θc.)

Instead of adding the signed squared in-phase component DI_(i) outputfrom the in-phase multiplier 421 a and the signed squared orthogonalcomponent DQ_(i) output from the orthogonal multiplier 421 b, andoutputting a result straight, the adder 427 may convert the result ofthe addition into an absolute value, then multiply the sign {±1} of theresult of the addition to the square root of the result of the additionconverted into the absolute value, and then output this multiplied valueas the squared addition signal A_(i). Similarly, instead of subtractingthe signed squared in-phase component DI_(i) output from the in-phasemultiplier 421 a from the signed squared orthogonal component DQ_(i)output from the orthogonal multiplier 421 b or vice versa, andoutputting a result straight, the subtracter 428 may convert the resultof the subtraction into an absolute value, then multiply the sign {±1}of the result of the subtraction to the square root of the result of thesubtraction converted into the absolute value, and then output thismultiplied value as the squared subtraction signal S_(i). When suchaddition or subtraction is performed, it is necessary to carry out thecalculation of obtaining the squared root, and the circuit becomescomplex. However, there is an advantage that the preambledetecting/timing phase difference calculating unit 423 at the latterstage can calculate the timing phase difference in higher precision.

The squared-addition signal component correlation calculating unit 429 acalculates correlation between the squared addition signal and the ½symbol frequency component exp[−jπ(fs)t]. Specifically, thesquared-addition signal component correlation calculating unit 429 aperforms the calculation shown in the equations (24a) and (24b) usingthe data string A_(i) (i=1, 2, 3, . . . ):

Ac _(i) =A _(i)×cos πi/2  (24a)

As _(i) =A _(i)×sin πi/2  (24b)

Subsequently, the squared-addition signal component correlationcalculating unit 429 a calculates an averages of the data strings(Ac_(i), As_(i)) obtained through the calculation in the equations (24a)and (24b), and outputs addition correlation signals (CA_(i), SA_(i)). Inthe equations (24a) and (24b), cos πi/2=1, 0, −1, 0, . . . , and sinπi/2=0, 1, 0, −1, . . . . Therefore, it is possible to obtain theaddition correlation signals (CA_(i), SA_(i)) easily. For example, whenaveraging with four symbols, the addition correlation signals (CA_(i),SA_(i)) can be obtained through the equations (24c) and (24d) asfollows:

CA _(i)=(A _(i) −A _(i+2) +A _(i+4) −A _(i+6) +A _(i+8) −A _(i+10) +A_(i+12) −A _(i+14))/8  (24c)

SA _(i)=(A _(i+1) −A _(i+3) +A _(i+5) −A _(i+7) +A _(i+9) −A _(i+11) +A_(i+13) −A _(i+15))/8  (24d)

Similarly, the squared-subtraction signal component correlationcalculating unit 429 b calculates correlation between the squaredsubtraction signal and the ½ symbol frequency component exp[−jπ(fs)t].Specifically, the squared-subtraction signal component correlationcalculating unit 429 b performs the calculation shown in the equations(25a) and (25b) using the data string S_(i) (i=1, 2, 3, . . . ):

Sc _(i) =S _(i)×cos πi/2  (25a)

Ss _(i) =S _(i)×sin πi/2  (25b)

Subsequently, the squared-subtraction signal component correlationcalculating unit 429 b calculates an averages of the data strings(Sc_(i), Ss_(i)) obtained through the calculation in the equations (25a)and (25b), and outputs subtraction correlation signals (CS_(i), SS_(i)).In the equations (25a) and the equation (25b), cos πi/2=1, 0, −1, 0, . .. , and sin πi/2=0, 1, 0, −1, . . . . Therefore, it is possible toobtain the subtraction correlation signals (CS_(i), SS_(i)) easily. Forexample, when averaging with four symbols, the subtraction correlationsignals (CS_(i), SS_(i)) can be obtained from the equation (25c) and theequation (25d) as follows:

CS _(i)=(S _(i) −S _(i+2) +S _(i+4) −S _(i+6) +S _(i+8) −S _(i+10) +S_(i+12) −S _(i+14))/8  (25c)

SS _(i)=(S _(i+1) −S _(i+3) +S _(i+5) −S _(i+7) +S _(i+9) −S _(i+11) +S_(i+13) −S _(i+15))8  (25d)

During the reception of the preamble symbol, when the carrier phase θc[deg] is within the range of (90<θc<180) or (270<θc<360) as shown inFIG. 22, for example, the amplitude of the squared subtraction signalS_(i) is larger than the amplitude of the squared addition signal A_(i).The absolute value of this takes a constant value E²=||I_(i)|²+|Q_(i)|²|regardless of the carrier phase θc. Therefore, the vector length of thesubtraction correlation signals (CS_(i), SS_(i)) becomes larger than thevector length of the addition correlation signals (CA_(i), SA_(i)), andthis also takes a constant value. For example, the correlation signals(CA_(i), SA_(i)) and (CS_(i), SS_(i)) obtained by sampling the preamblesymbols shown in FIG. 22 at the timings shown in FIG. 10 become as shownin FIG. 12, and the vector length of the subtraction correlation signalsbecomes larger.

Further, during the reception of the preamble symbol, when the carrierphase θc [deg] is within the range of (0<θc<90) or (180<θc<270) as shownin FIG. 25, for example, the amplitude of the squared addition signalA_(i) is larger than the amplitude of the squared subtraction signalS_(i). The absolute value of this takes a constant valueE²=||I_(i)|²+|Q_(i)|²| regardless of the carrier phase θc. Therefore,the vector length of the addition correlation signals (CA_(i), SA_(i))becomes larger than the vector length of the subtraction correlationsignals (CS_(i), SS_(i)), and this also takes a constant value. Forexample, the correlation signals (CA_(i), SA_(i)) and (CS_(i), SS_(i))obtained by sampling the preamble symbols shown in FIG. 25 at thetimings shown in FIG. 11 become as shown in FIG. 13, and the vectorlength of the addition correlation signals becomes larger.

On the other hand, during a reception when there is no signal (receivingonly noise in the absence of a signal) or during the reception of asignificant data section that follows the preamble, the vector shows asmaller length, as the ½ symbol frequency component does not exist for along time in the addition correlation signals (CA_(i), SA_(i)) and thesubtraction correlation signals (CS_(i), SS_(i)).

The vector selecting unit 430 selects signals having a larger vectorlength from the addition correlation signals (CA_(i), SA_(i)) and thesubtraction correlation signals (CS_(i), SS_(i)), and outputs theselected signals as selected correlation signals (CO_(i), SO_(i)).

The detailed operation of the above will be explained based on FIG. 9.The maximum absolute value detecting unit 431 obtains maximum values of|CA_(i)|, |SA_(i)|, |CS_(i)|, and |SS_(i)| that are the absolute valuesof the addition correlation signals (CA_(i), SA_(i)) and the subtractioncorrelation signals (CS_(i), SS_(i)) respectively, like in the case ofthe conventional vector combination selecting unit 406 shown in FIG. 21.

When the maximum value obtained by the maximum absolute value detectingunit 431 is either |CA_(i)| or |SA_(i)|, the selecting unit 432 selectsthe addition correlation signals (CA_(i), SA_(i)). When the maximumvalue obtained is either |CS_(i)| or |SS_(i)|, the selecting unit 432selects the subtraction correlation signals (CS_(i), SS_(i)). Theselecting unit 432 outputs the selected signals as the selectedcorrelation signals (CO_(i), SO_(i)).

Specifically, the operation of the vector selecting unit 430 during thereception of the preamble symbol is as follows.

When the carrier phase θc [deg] is within the range of (90<θc<180) or(270<θc<360) as shown in FIG. 22, the vector length of the subtractioncorrelation signals (CS_(i), SS_(i)) becomes larger than the vectorlength of the addition correlation signals (CA_(i), SA_(i)) as shown inFIG. 12. Therefore, the vector selecting unit 430 selects thesubtraction correlation signals (CS_(i), SS_(i)), and outputs theselected correlation signals (CO_(i), SO_(i))=(CS_(i), SS_(i)). On theother hand, when the carrier phase θc [deg] is within the range of(0<θc<0) or (180<θc<270) as shown in FIG. 25, the vector length of theaddition correlation signals (CA_(i), SA_(i)) becomes larger than thevector length of the subtraction correlation signals (CS_(i), SS_(i)) asshown in FIG. 13. Therefore, the vector selecting unit 430 selects thesubtraction correlation signals (CA_(i), SA_(i)), and outputs theselected correlation signals (CO_(i), SO_(i))=(CA_(i), SA_(i)).

Further, when the carrier phase θc [deg] is within the range of(90<θc<180) or (270<θc<360), the vector length shown by the subtractioncorrelation signals (CS_(i), SS_(i)) shows a constant value regardlessof the carrier phase θc. When the carrier phase θc [deg] is within therange of (0<θc<90) or (180<θc<270), the vector length represented by theaddition correlation signals (CA_(i), SA_(i)) is constant regardless ofthe carrier phase θc. Therefore, the vector length represented by theselected correlation signals (CO_(i), SO_(i)) output from the vectorselecting unit 430 during the reception of the preamble is alwaysconstant and large value regardless of the carrier phase θc.

On the other hand, during the reception when there is no signal(receiving only noise in the absence of a signal) or during thereception of a significant data section that follows the preamble, thevector selecting unit 430 selects at random either the additioncorrelation signals (CA_(i), SA_(i)) that take a small vector length orthe subtraction correlation signals (CS_(i), SS_(i)) that take a smallvector length. Therefore, in this case, the vector length shown by theselected correlation signals (CO_(i), SO_(i)) takes a small value.

The selected correlation signals (CO_(i), SO_(i)) are sent to thepreamble detecting/timing phase difference calculating unit 423 a, andthe following two calculations are carried out simultaneously.

The first calculation is of obtaining a vector length V_(i) of theselected correlation signals (CO_(i), SO_(i)) from the equation (26):

V _(i)=(|CO _(i)|² +SO _(i)|²)^(1/2)  (26)

The other calculation is of obtaining a vector angle of the selectedcorrelation signals (CO_(i), SO_(i)) from the equation (27):

θo _(i)=tan⁻¹(SO _(i) /CO _(i))  (27)

In the above equation, θo_(i) is a timing phase difference when thenormalization has been carried out in the 2 symbol period (2T), likeθ_(T). Therefore, a timing phase difference θr_(i) [deg] when thenormalization has been carried out in the symbol period (T) is obtainedfrom the equation (23).

During the reception of the preamble symbol, the vector length V_(i)represented by the subtraction correlation signals (CS_(i), SS_(i)) is aconstant and large value regardless of the carrier phase θc. Further,the timing phase difference θr_(i) [deg] also takes a certain value. Forexample, when the preamble signals shown in FIG. 22 are sampled at thetimings of vertical lines shown in FIG. 10, the subtraction correlationsignals (CS_(i), SS_(i)) in FIG. 12 are selected by the vector selectingunit 430. The vector length of these signals becomes V_(i), and thevector angle becomes θo_(i).

On the other hand, when the preamble signals shown in FIG. 25 aresampled at the timings of vertical lines shown in FIG. 11 that are thesame timings as those in FIG. 10, the addition correlation signals(CA_(i), SA_(i)) in FIG. 13 are selected by the vector selecting unit430. The vector length of these signals becomes V_(i), and the vectorangle becomes θo_(i). There is a difference of 180 [deg] between theθo_(i) shown in FIG. 12 and the θo_(i) shown in FIG. 13. However, basedon the processing of the equation (23), θr_(i) obtained from the θo_(i)in FIG. 12 and θr_(i) obtained from the θo_(i) in FIG. 13 coincide witheach other.

On the other hand, during the reception when there is no signal(receiving only noise in the absence of a signal) or during thereception of a significant data section that follows the preamble, thevector length V_(i) shows a small value, and the timing phase differenceθr_(i) [deg] also takes an uncertain value. The relationship between theV_(i) according to the reception status and the certainty of the θr_(i)becomes as shown in FIG. 5.

Therefore, the preamble detecting/timing phase difference calculatingunit 423 a can obtain the timing error τ based on the followingprocessing, even when the reception timing of the burst signal isunknown and also when the arrival time of the preamble is unknown.

In other words, when a vector length V_(i) is large as a result ofmonitoring V_(i) (for example, when the vector length V_(i) exceeds acertain threshold value εp), a decision is made as “preamble is beingreceived”, and the timing phase difference θr_(i) [deg] is latched atthe timing shown in FIG. 5. As is clear from FIG. 5, the latched timingphase difference θr_(i) [deg] is a timing phase difference θr_(i) [deg]when V_(i) is large. Therefore, this is a certain value. The preambledetecting/timing phase difference calculating unit 423 a obtains thetiming errors from the equations (16a) and (16b) using the timing phasedifference θs obtained as described above, and gives a phase controlsignal for canceling the timing error τ to the VCO 401 at the latterstage.

Under this structure, the magnitude (=vector length V_(i)) of theselected correlation signals (CO_(i), SO_(i)) is constant regardless ofthe carrier phase θc, like in the first embodiment. Therefore, thepreamble detection characteristics for detecting the vector length V_(i)based on the threshold value εp are not influenced by the carrier phaseθc.

When the reception timing of the burst signal is known and also when thearrival time of the preamble can be specified, the preamble detectionoperation is not necessary. Therefore, in this case, it is possible touse the conventional timing phase difference calculating unit 402 inplace of the preamble detecting/timing phase difference calculating unit423 a. In this case, as the function of obtaining the vector lengthV_(i) and detecting its magnitude is not necessary, it is possible toreduce the circuit scale.

The VCO 401 receives the phase control signal from the preambledetecting/timing phase difference calculating unit 423 a, controls thephases of the regeneration sample clock and the regeneration symbolclock, and sets the timing error τ to “0”.

Under this structure, it is not necessary to use the vector combinationselecting unit 405 for carrying out a complex processing. Therefore, itis possible to reduce the circuit scale.

Further, like in the first embodiment, the timing regenerating device400 in the fourth embodiment can carry out the estimation of a timingphase and the detection of a preamble at high precision regardless of acarrier phase, when the preamble symbol is a signal that alternatelyshifts between two points for each one symbol on a complex plane, likethe preamble symbol that alternately shifts between two adjacent Nyquistpoints for each symbol on the complex plane as shown in FIG. 36, inaddition to the preamble symbol that alternately shifts between twoNyquist points for each symbol that become symmetrical with the origin(that shifts ±180 [deg] for each symbol) on the complex plane as shownin FIG. 22.

FIG. 14 is a structure diagram of a demodulator according to a fifthembodiment of the present invention. This demodulator has a feedbacksystem circuit called a PLL (Phase Lock Loop) as shown in FIG. 6 builtinto the demodulator shown in FIG. 8. Sections identical to orcorresponding to the portions of the demodulator shown in FIG. 6 andFIG. 8 are attached with the same reference numbers.

The demodulator comprises a PLL timing regenerating unit which includesthe phase detecting unit 424, averaging unit 425, and VCO 401 a.

The operation of the demodulator according to a fifth embodiment willnow be explained. First, the phase detecting unit 424, the averagingunit 425, and the VCO 401 a are operated at the time of detecting apreamble or at the time of calculating a timing error τ. The processingperformed by the sections from the in-phase component square calculationunit 420 a, orthogonal component square calculation unit 420 b up to thepreamble detecting/timing phase difference calculating unit 423 a issimilar to that of the demodulator shown in FIG. 8. When a preamblesymbol has been detected, a clock phase control for canceling the timingerror τ obtained at the same time as this detection is given to the VCO401 a as a phase control signal.

The phase detecting unit 424 detects whether a timing phase is advancedor delayed from received data (I_(i), Q_(i)). When the timing phase isadvanced as a detection signal, “+1” is output, and when the timingphase is delayed, “−1” is output.

The averaging unit 425 receives this advance/delay signal, calculates anaverage of the signals using a random work filter, for example, andoutputs the obtained value as a phase advance/delay signal.

The VCO 401 a controls the phases of a regeneration sample clock and aregeneration symbol clock based on this phase advance/delay signal. Whenthis phase advance/delay signal is “positive”, the VCO 401 a advancesthe timing phase, and when the phase advance/delay signal is “negative”,the VCO 401 a delays the timing phase. The VCO 401 a is usuallycontrolled based on the phase advance/delay signal. However, when apreamble has been detected and also when a phase control signal has beeninput, the VCO 401 a controls each clock phase by using the phasecontrol signal without using the phase advance/delay signal.

According to this structure, it is possible to realize the tracing ofthe timing phase during the reception of the significant random datawhile carrying out the estimating and control of the timing phase athigh precision using a short preamble symbol.

Further, like the timing regenerating device shown in FIG. 8, the timingregenerating device 400 shown in FIG. 14 can carry out the estimation ofa timing phase and the detection of a preamble at high precisionregardless of a carrier phase, when the preamble symbol is a signal thatalternately shifts between two points for each one symbol on a complexplane, like the preamble symbol that alternately shifts between twoadjacent Nyquist points for each symbol on the complex plane as shown inFIG. 36, in addition to the preamble symbol that alternately shiftsbetween two Nyquist points for each symbol that become symmetrical withthe origin (that shifts ±180 [deg] for each symbol) on the complex planeas shown in FIG. 22.

FIG. 15 is a structure diagram of a demodulator according to a sixthembodiment of the present invention. A feedforward type timingregenerating device as shown in FIG. 7 is used in place of the VCO 401in the demodulator shown in FIG. 8. Sections identical to orcorresponding to the portions of the demodulator shown in FIG. 7 andFIG. 8 are attached with the same reference numbers.

The demodulator also comprises oscillator 426, data interpolating unit600, and data deciding unit 500 a.

Operation of the demodulator according to a sixth embodiment will now beexplained. The oscillator 426 outputs an asynchronous sample clock thatself-runs at two times the symbol period. The first A/D converter 301 aand second A/D converter 301 b asynchronously sample the data at 2[sample/symbol] by this asynchronous sample clock. The in-phasecomponent square calculation unit 420 a, orthogonal component squarecalculation unit 420 b, in-phase multiplier 421 a, orthogonal multiplier421 b, adder 427, and subtracter 428 carry out a series of signalprocessing of the asynchronously sampled received data (I_(i), Q_(i)).

The squared-addition signal component correlation calculating unit 429 acalculates correlation between a squared addition signal A_(i) outputfrom the adder 427 and a ½ frequency component exp[−jπ(fs)t] of a symbolfrequency output from the oscillator 426. Then, the squared-additionsignal component correlation calculating unit 429 a averages this andoutputs addition correlation signals (CA_(i), SA_(i)). Similarly,squared-subtraction signal component correlation calculating unit 429 bcalculates correlation between a squared subtraction signal S_(i) outputfrom the subtracter 428 and a ½ frequency component exp[−jπ(fs)t] of asymbol frequency output from the oscillator 426. Then, thesquared-subtraction signal component correlation calculating unit 429 baverages this and outputs addition correlation signals (CS_(i), SS_(i)).

Next, vector selecting unit 430 and preamble detecting/timing phasedifference calculating unit 423 process the addition correlation signals(CA_(i), SA_(i)) and the subtraction correlation signals (CS_(i),SS_(i)), thereby to obtain a timing error τ.

The data interpolating unit 600 interpolates the received data (I_(i),Q_(i)) obtained by asynchronous 2 [sample/symbol], generates a receiveddata having a time resolution of {fraction (1/16)} of the symbol period,for example, and outputs the interpolated received data.

The data deciding unit 500 a extracts a Nyquist point of theinterpolated received data using the information of the timing error τoutput from the preamble detecting/timing phase difference calculatingunit 423 a, and outputs the data of the extracted Nyquist point asdemodulated data.

As explained above, based on the use of the low-cost and compactoscillator 426 in place of the VCO having a large circuit scale, it ispossible to make the demodulator compact. at low cost.

Further, the timing regenerating device 400 shown in FIG. 15 can carryout the estimation of a timing phase and the detection of a preamble athigh precision regardless of a carrier phase, when the preamble symbolis a signal that alternately shifts between two points for each onesymbol on a complex plane, like the preamble symbol that alternatelyshifts between two adjacent Nyquist points for each symbol on thecomplex plane as shown in FIG. 36, in addition to the preamble symbolthat alternately shifts between two Nyquist points for each symbol thatbecome symmetrical with the origin (that shifts ±180 [deg] for eachsymbol) on the complex plane as shown in FIG. 22.

FIG. 16 is a structure diagram of a demodulator according to a seventhembodiment of the present invention. This demodulator is such that, inthe demodulator shown in FIG. 8, timing regeneration is carried outusing not only a preamble symbol but also using a random pattern signalthat follows the preamble symbol. Sections identical to or correspondingto the portions of the demodulator shown in FIG. 8 are attached with thesame reference numbers.

The basic concept of the seventh embodiment is to extract a ½ symbolfrequency component that exists in burst in time unit of a few symbolsin the random pattern signal that follows the preamble, average theextracted components, and use the result for estimating a timing phase.

It is possible to utilize a ½ symbol frequency component that existsduring a short period time of a few symbols in the random patternsignal. Taking the QPSK modulation system, for example, there exists a ½symbol frequency component in the 8-bit data string of the following 12patterns. The probability that any one of these occurs is as small as{fraction (12/256)}=4.6%. However, when ½ symbol frequency componentsincluded in these patterns are detected, and the detected ½ symbolfrequency components are averaged over a long period of time, it ispossible to realize the estimation of a timing phase at high precision.

Pattern A: 11001100

Pattern B: 00110011

Pattern C: 01100110

Pattern D: 10011001

Pattern E: 11011101

Pattern F: 01110111

Pattern G: 11101110

Pattern H: 10111011

Pattern I: 01000100

Pattern J: 00010001

Pattern K: 10001000

Pattern L: 10001000

Further, according to the timing regenerating device shown in FIG. 16,when the AGC (Automatic Gain Control) is used at the same time forcontrolling the signal level of the reception signal, it is possible tocarry out a timing regeneration without receiving an influence of anover-amplified signal that is input due to the operation of the AGC.

This demodulator comprises the weighting unit 433, averaging unit 434,and phase detecting unit 435.

Operation of the demodulator according to the seventh embodiment willnow be explained. The operation performed by the components from theantenna 100 up to adder 427 and subtracter 428 is similar to that of thedemodulator shown in FIG. 8.

The squared-addition signal component correlation calculating unit 429 acalculates correlation between the squared addition signal and a ½symbol frequency component exp[−jπ(fs)t]. Specifically, thesquared-addition signal component correlation calculating unit 429 aobtains a data string (Ac_(i), As_(i)) from the equations (24a) and(24b), calculates an averages of the data string, and outputs additioncorrelation signals (CA_(i), SA_(i)). Similarly, squared-subtractionsignal component correlation calculating unit 429 b calculatescorrelation between the squared subtraction signal and a ½ symbolfrequency component exp[−jπ(fs)t]. Specifically, the squared-subtractionsignal component correlation calculating unit 429 b obtains a datastring (Sc_(i), Ss_(i)) from the equations (25a) and (25b), calculatesan averages of the data sting, and outputs addition correlation signals(CS_(i), SS_(i)).

However, for averaging the data string, a small number of data like foursymbols, 8 symbols, or 12 symbols are used. For example, in the case ofobtaining a correlation with any one of the 8-bit patterns from thepatterns A to L, continuous eight data are used for the averaging.

The vector selecting unit 430 selects signals having a larger vectorlength from the addition correlation signals (CA_(i), SA_(i)) and thesubtraction correlation signals (CS_(i), SS_(i)), and outputs theselected signals as selected correlation signals (CO_(i), SO_(i)).

The weighting unit 433 calculates vector length VO_(i) of the selectedcorrelation signals (CO_(i), SO_(i)) which are output by the vectorselecting unit 430, and obtains a weight according to the magnitude ofthis VO_(i). Next, the weighting unit 433 multiplies the weight α to theselected correlation signals (CO_(i), SO_(i)) based on the equations(27a) and (27b), and outputs a result of this weighting as weightedcorrelation signals (CW_(i), SW_(i)):

CW _(i) =αCOi  (27a)

SW _(i) =αSOi  (27b)

When the patterns A to D have been received, the vector length VO_(i)has a very large value, and when the pattern E to the pattern L havebeen received, the vector length VO_(i) has a large value. When otherpattern has been received, the vector length VO_(i) shows a small value.

Therefore, as the weighting unit 433 carries out the weighting accordingto the vector length VO_(i) (a smaller weighting when VO_(i) is smaller)based on the equations (27a) and (27b), it is possible to extract onlythe correlation information when the patterns A to L have been received.

For example, three values are detected for VO_(i) based on two thresholdvalues, and the weight is set as follows:

when VO_(i) has a very large value; α=1

when VO_(i) has a large value; α=½

when VO_(i) has a small value; α=0

Based on this setting, the selected correlation signals (CO_(i), SO_(i))having uncertain timing phase information other than the patterns A to Lare not output to the averaging unit at the latter stage. Among thepatterns A to L, the patterns A to D include many symbol frequencycomponents as compared with the patterns E to L. However, during thereception of these patterns A to D, a large weight is placed. Therefore,it is possible to efficiently carry out the extraction of the ½ symbolfrequency components that are effective for estimating the timing phase.

When a limiter amplifier is used for controlling the signal level of thereception signal, the above-described weighting processing may becarried out. However, when the AGC amplifier is used for controlling thesignal level of the reception signal, the timing phase error increasesas the signal that exceeds the input range of the A/D converter is inputat time of leading the AGC. In this case, the following weightingprocessing is carried out.

First, in the steady status of the AGC, a vector length VE of theweighted correlation signals (CW_(i), SW_(i)) obtained when the preamblesymbol is input is obtained in advance. Then, VO_(i) is compared withVE. When VO_(i) is larger than VE, a decision is made that a distortedsignal due to the over-amplification has been input in the process ofleading the AGC. Then, when the difference (VO_(i)−VE) is larger, asmaller weight is applied (α is set to a small value).

When VO_(i) is substantially equal to VE, a largest weight is applied (αis set to a maximum value).

Further, when VO_(i) is smaller than VE, a smaller weight is applied asthe difference (VE−VO_(i)) is larger (α is set to a small value).

Based on the weighting, it becomes possible to normally estimate thetiming phase when inputting an over-amplified signal that can begenerated due to the operation of the AGC, simultaneously with theestimating of the timing phase of the random pattern.

The weighted correlation signals (CW_(i), SW_(i)) thus obtained areinput into the averaging unit 434. The averaging unit 434 calculates anaverage of the weighted correlation signals (CT_(i), ST_(i)) that areobtained after multiplying the weighted correlation signals (CW_(i),SW_(i)) by two times (θA_(i)=2θW_(i) mod 360 [deg]) based on theequation (28), when the vector angle of the weighted correlation signals(CW_(i), SW_(i)) is expressed as θW_(i) [deg], and the vector length isexpressed as θV_(i):

(CT _(i) , ST _(i))=(θV _(i) cos θA _(i) , θV _(i) sin θA _(i))  (28)

where, θA_(i) [deg]=(2θW_(i) mod 360) [deg].

Based on the processing of the equation (28), it is possible to convertthe weighted correlation signals (CW_(i), SW_(i)) that can generate twoways of the vector angles θW_(i)={θW_(i), θW_(i)+180} [deg] depending onthe data pattern into signals (CT_(i), ST_(i)) having one vector angleθA_(i). This makes it possible to normally carry out the subsequentaveraging processing.

The averaging unit 434 calculates an average of the weighted correlationsignals (CT_(i), ST_(i)) to obtain averaged signals (ΣCT_(i), ΣST_(i)),and outputs the averaged signals (ΣCT_(i), ΣST_(i)).

The averaging of (CT_(i), ST_(i)) can be realized by an FIR (FiniteImpulse Response) filter or an IIR (Infinite Impulse Response) filter,for example. In this case, the characteristics of the timingregenerating device are different depending on the time constant (band)of each filter. When the time constant is made larger (when the band ismade narrower), it is possible to realize the high stabilization of thetiming phase (low phase jitter). When the time constant is made smaller(when the band is made wider), it is possible to realize the high-speedleading of the timing phase (low phase jitter). Therefore, when the timeconstant is changed over such that the time constant is small during thereception of the preamble symbol and the time constant is large duringthe reception of the subsequent random pattern, it is possible torealize both the high-speed leading of the timing phase within thepreamble and the low-phase jitter during the reception of the randompattern.

Further, when the frame timing is unknown and also when the timing ofchanging over the time constant of the filter is unknown, the averagingprocessing is carried out as follows. The weighted correlation signals(CT_(i), ST_(i)) of which vector angles have been converted are averagedin the following procedure, thereby to realize both the high-speedleading and the low-phase jitter.

When a vector length ΣV_(i) shown by (ΣCT_(i), ΣST_(i)) is equal to orlower than a threshold value Σε, the input data is accumulated as shownin the following equations (29a) and (29b):

 ΣCT _(i) =ΣCT _(i−1) +CT _(i)  (29a)

ΣST _(i) =ΣST _(i−1) +ST _(i)  (29b)

Further, when a vector length ΣV_(i) represented by (ΣCT_(i), ΣST_(i))is larger than a certain threshold value Σε, these operate as IIRfilters as shown in the following equation (30a) and the equation (30b)(where β represents an oblivion coefficient (1>β>0)). The time constantof the IIR filter becomes a small value of about a half of the preamblelength, for example:

ΣCT _(i) =βΣCT _(i−1) +CT _(i)  (30a)

ΣST _(i) =βΣST _(i−1) +ST _(i)  (30b)

When the preamble symbol has been input; the input weighted correlationsignals (CT_(i), ST_(i)) take large values. Therefore, the vector lengthΣV_(i) exceeds the threshold value Σε, and the accumulation processingshown in the equations (29a) and (29b) is promptly changed over to theIIR filtering as shown in the equations (30a) and (30b).

When the subsequent random pattern has been received, the input weightedcorrelation signals (CT_(i), ST_(i)) have small values. Therefore, thevector length ΣV_(i) become smaller than the threshold value Σε, and theIIR filtering as shown in the equations (30a) and (30b) is promptlychanged over to the accumulation processing shown in the equations (29a)and (29b).

When the operation is carried out based on only the integrationaccording to the equations (29a) and (29b), an overflow occurs. On theother hand, when the operation is carried out based on only the IIRfiltering according to the equations (30a) and (30b), the vector lengthΣV_(i) become smaller during the reception of the random pattern and thetiming phase jitter increases. However, when the above-describedchangeover processing is carried out, at the input time of the preamblesymbol, a high-speed timing phase leading is realized according to theequations (30a) and (30b) without generating an overflow based on theIIR filtering. During the reception of the subsequent random pattern,the processing is changed over to the integration processing accordingto the equations (29a) and (29b). Therefore, it is possible to hold alarge vector length ΣV_(i) obtained during the reception of the preamblewithout lowering this vector length. As a result, it is also possible torealize a lower jitter of the timing phase during the reception of therandom pattern.

It is necessary to determine the threshold value Σε corresponding to βthat determines the time constant of the IIR filter.

The processing for obtaining the vector length ΣV_(i) is complex ascompared with the squaring processing and the square root calculationprocessing. Therefore, in place of the vector length ΣV_(i), it ispossible to use MV_(i)=max(|ΣCT_(i)|, |ΣST_(i)|) that is obtained basedon a relatively simple processing, and change over the processing of theequations (29a) and (29b) with the processing of the equations (30a) and(30b) based on a result of the comparison between MV_(i) and thethreshold value Σε.

The timing phase difference calculating unit 435 obtains the vectorangle shown by the averaged weighted correlation signals (ΣCT_(i),ΣST_(i)) as the timing phase difference θs [deg] from the followingequation (31):

θ_(2s)=tan⁻¹(ΣCT _(i) /ΣST _(i))  (31)

Then, the timing phase difference calculating unit 435 substitutes thetiming phase difference θs [deg] into the equations (16a) and (16b),thereby to obtain the timing error τ.

This timing phase difference calculating unit 435 is different from theconventional timing phase difference calculating unit 402 shown in FIG.20 in that the timing phase difference calculating unit 435 carries outthe processing of the equation (15). The averaging unit 434 carries outthe processing of the equation (28) at a front stage as the processingcorresponding to the equation (15).

Next, the timing phase difference calculating unit 435 supplies theobtained timing error τ to the VCO 401 provided at the latter stage inthe symbol period of X (where X is a range of a few symbols to ten oddsymbols), and also carries out the control of the equations (32a) and tothe averaging unit 434:

ΣCT _(i) =ΣV _(i)  (32a)

ΣST _(i)=0  (32b)

Based on this control, it is possible to realize not a one-time phasecontrol but a continuous phase control.

The VCO 401 receives the phase control signal from the timing phasedifference calculating unit 435, controls the phases of the regenerationsample clock and the regeneration symbol clock, and sets the timingerror τ to “0”.

Based on the above arrangement, it is possible to realize the tracing ofthe timing phase during the reception of the significant random datawhile carrying out the estimating and control of the timing phase athigh precision using a short preamble symbol.

Further, when the AGC (Automatic Gain Control) is used for controllingthe level of the reception signal, it is possible to carry out thetiming regeneration at high precision without an increase in the errorof estimating the timing phase, when the reception signal over-amplifiedby the AGC has been input.

Further, like in the first embodiment, the timing regenerating device400 in the seventh embodiment can carry out the estimation of a timingphase and the detection of a preamble at high precision regardless of acarrier phase, when the preamble symbol is a signal that alternatelyshifts between two points for each one symbol on a complex plane, likethe preamble symbol that alternately shifts between two adjacent Nyquistpoints for each symbol on the complex plane as shown in FIG. 35, inaddition to the preamble symbol that alternately shifts between twoNyquist points for each symbol that become symmetrical with the origin(that shifts ±180 [deg] for each symbol) on the complex plane as shownin FIG. 22.

FIG. 17 is a structure diagram of a demodulator according to an eighthembodiment of the present invention. A feedforward type timingregenerating device as shown in FIG. 7 is used in place of the VCO 401in the demodulator shown in FIG. 16. Sections identical to orcorresponding to the portions of the demodulator shown in FIG. 7 andFIG. 16 are attached with the same reference numbers. This demodulatorcomprises the oscillator 426, data interpolating unit 600, and datadeciding unit 500 a.

Operation of demodulator according to the eighth embodiment will now beexplained. First, the oscillator 426 outputs an asynchronous sampleclock that self-runs at two times the symbol period. The first A/Dconverter 301 a and second A/D converter 301 b asynchronously sample thedata at 2 [sample/symbol] by this asynchronous sample clock.Subsequently, the in-phase component square calculation unit 420 a,orthogonal component square calculation unit 420 b, in-phase multiplier421 a, orthogonal multiplier 421 b, adder 427, and subtracter 428 carryout a signal processing of the asynchronously sampled received data(I_(i), Q_(i)).

The squared-addition signal component correlation calculating unit 429 acalculates correlation between a squared addition signal A_(i) outputfrom the adder 427 and a ½ frequency component exp[−jπ(fs)t] of a symbolfrequency output from the oscillator, and outputs addition correlationsignals (CA_(i), SA_(i)). Similarly, the squared-subtraction signalcomponent correlation calculating unit 421 b calculates correlationbetween a squared subtraction signal S_(i) output from the subtracter428 b and a ½ frequency component exp[−jπ(fs)t] of a symbol frequencyoutput from the oscillator 426, and outputs subtraction correlationsignals (CS_(i), SS_(i)).

The vector selecting unit 430, weighting unit 433, and averaging unit434 process to obtain averaged weighted correlation signals (ΣCT_(i),ΣST_(i)) The timing phase difference calculating unit 435 a obtains thetiming phase difference θs [deg] from the equation (31) using theaveraged weighted correlation signals (ΣCT_(i), ΣST_(i)). The timingphase difference calculating unit 435 a also substitutes the timingphase difference θs [deg] into the equations (16a) and (16b), thereby toobtain the timing error τ.

This timing phase difference calculating unit 435 a is different fromthe timing phase difference calculating unit 435 shown in FIG. 16 inthat the timing phase difference calculating unit 435 a does not carryout the calculations of the equations (32a) and (32b) that are processedin the X [symbol] period. The calculation in the equations (32a) and(32b) is necessary only when the integration filters of the FIR type andthe IIR type are used continuously in the feedback type timingregeneration system. This processing is not necessary in the feedforwardtype timing regeneration system.

The data interpolating unit 600 interpolates received data (I_(i),Q_(i)) obtained by asynchronous 2 [sample/symbol], generates a receiveddata having a time resolution of {fraction (1/16)} of the symbol period,for example, and outputs the interpolated received data.

The data deciding unit 500 a extracts a Nyquist point of theinterpolated received data using the information of the timing error τoutput from the timing phase difference calculating unit 435 a, andoutputs the data of the extracted Nyquist point as demodulated data.

As explained above, based on the use of the low-cost and compactoscillator 426 in place of the VCO having a large circuit scale, it ispossible to make the demodulator compact at low cost.

Further, like in the first embodiment, the timing regenerating device400 in the eighth embodiment can carry out the estimation of a timingphase and the detection of a preamble at high precision regardless of acarrier phase, when the preamble symbol is a signal that alternatelyshifts between two points for each one symbol on a complex plane, likethe preamble symbol that alternately shifts between two adjacent Nyquistpoints for each symbol on the complex plane as shown in FIG. 35, inaddition to the preamble symbol that alternately shifts between twoNyquist points for each symbol that become symmetrical with the origin(that shifts ±180 [deg] for each symbol) on the complex plane as shownin FIG. 22.

FIG. 18 is a structure diagram of an averaging unit in a demodulatoraccording to a ninth embodiment of the present invention. According tothe demodulator in the seventh embodiment shown in FIG. 16 and thedemodulator in the eighth embodiment shown in FIG. 17, the doublingprocessing shown in the equation (28) is carried out by the averagingunit 434. However, in the ninth embodiment, the processing of theaveraging unit 434 is changed in order to avoid the complex calculationand the occurrence of an error (multiplication loss) due to the doublingprocessing. In the demodulator using the averaging unit in FIG. 18, theconventional timing phase difference calculating unit 402 is used inplace of the timing phase difference calculating unit 435 or the timingphase difference calculating unit 435 a.

The averaging unit comprises the first correlation signal generatingunit 436 a, second correlation signal generating unit 436 b, firstcorrelation signal averaging unit 437 a, second correlation signalaveraging unit 437 b, correlation value comparing unit 438, andselecting unit 439.

Operation of the averaging unit according to the ninth embodiment willnow be explained. Weighted correlation signals (CW_(i), SW_(i)) areinput into the first correlation detecting unit 436 a and the secondcorrelation detecting unit 436 b.

The first correlation detecting unit 436 a outputs correlation signals(CT1 _(i), ST1 _(i)) based on the equations (33a) and (33b):

(CT 1 _(i) , ST 1 _(i))=(CW _(i) , SW ₁) when (CW _(i)≧0)  (33a)

(CT 1 _(i) , ST 1 _(i))=(−CW _(i) , −SW ₁) when (CW _(i)<0)  (33b)

The second correlation detecting unit 436 b outputs correlation signals(CT2 _(i), ST2 _(i)) from the equation (34a) and the equation (34b):

(CT 2 _(i) , ST 2 _(i))=(CW _(i) , SW ₁) when (SW _(i)≧0)  (34a)

(CT 2 _(i) , ST 2 _(i))=(−CW _(i) , −SW ₁) when (SW _(i)<0)  (34b)

The first correlation signal averaging unit 437 a calculates an averageof the correlation signals (CT1 _(i), ST1 _(i)), and outputs averagedcorrelation signals (ΣCT1 _(i), ΣST1 _(i)). Similarly, the secondcorrelation signal averaging unit 437 b calculates an average of thecorrelation signals (CT2 _(i), ST2 ₁), and outputs the averagedcorrelation signals (ΣCT2 _(i), ΣST2 _(i)). The averages of thecorrelation signals (CT1 _(i), ST1 _(i)) and the correlation signals(CT2 _(i), ST2 _(i)) are obtained using the equations (29a), (29b),(30a), and (30b).

When two ways of vector angles θW_(i) shown by the weighted correlationsignals (CW_(i), SW_(i)) are θW_(i)={0, 180} [deg], for example,correlation values (CW1 _(i), SW1 _(i)) do not converge to one point,but correlation values (CW2 _(i), SW2 _(i)) converge to one point.Therefore, the vector length ΣV2 _(i) of the correlation signals (ΣCT2_(i), ΣST2 _(i)) that are obtained by averaging (CW2 _(i), SW2 _(i))becomes larger than the vector length ΣV1 _(i) of the correlationsignals (ΣCT1 _(i), ΣST1 _(i)) that are obtained by averaging (CW1 _(i),SW1 _(i)).

Further, when θW_(i)={90, −90} [deg], for example, the correlationvalues (CW2 _(i), SW2 _(i)) do not converge to one point, but thecorrelation values (CW1 _(i), SW1 _(i)) converge to one point.Therefore, the vector length ΣV1 _(i) of the correlation signals (ΣCT1_(i), ΣST1 _(i)) that are obtained by averaging (CW1 _(i), SW1 _(i))becomes larger than the vector length ΣV2 _(i) of the correlationsignals (ΣCT2 _(i), ΣST2 _(i)) that are obtained by averaging (CW2 _(i),SW2 _(i)).

Further, when θW_(i)={45, −45, 135, −135} [deg], for example, both thecorrelation values (CW1 _(i), SW1 _(i)) and the correlation values (CW2_(i), SW2 _(i)) converge to one point. Therefore, the vector length ΣV1_(i) of the correlation signals (ΣCT1 _(i), ΣST1 _(i)) that are obtainedby averaging (CW1 _(i), SW1 _(i)) becomes equal to the vector length ΣV2_(i) of the correlation signals (ΣCT2 _(i), ΣST2 _(i)) that are obtainedby averaging (CW2 _(i), SW2 _(i)).

The correlation value comparing unit 438 compares the magnitudes of thevectors ΣV1 _(i) with ΣV2 _(i) shown by the correlation signals (ΣCT1_(i), ΣST1 _(i)) and the correlation signals (ΣCT2 _(i), ΣST2 _(i))respectively, and outputs a result of the comparison.

Based on the result of the comparison, the selecting unit 439 outputsthe correlation signals of a larger vector as the averaged correlationsignals (ΣCT_(i), ΣST_(i)). The equation (35a) and the equation (35b)represent this processing:

(ΣCT _(i) , ΣST _(i))=(ΣCT 1 _(i) , ΣST 1 _(i))(ΣV 1 _(i) ≧ΣV 2_(i))  (35a)

(ΣCT _(i) , ΣST _(i))=(ΣCT 2 _(i) , ΣST 2 _(i))(ΣV 1 _(i) <ΣV 2_(i))  (35b)

The timing phase difference calculating unit 403 handles the averagedcorrelation signals (ΣCT_(i), ΣST_(i)) as the combined correlationvalues (ΣC, ΣS) in a similar manner to that of the conventional method,and obtains a vector angle θ_(2s) represented by (ΣCT_(i), ΣST_(i)),substitutes this θ_(2s) into the equation (15), thereby to obtain atiming phase difference θs [deg] when the normalization is carried outin the symbol period (T). The relationship between the timing phasedifference θs and the timing error τ is as shown in the equations (16a)and (16b).

The timing phase difference calculating unit 403 outputs a phase controlsignal for canceling the timing error τ from the timing error τ obtainedby the above calculation.

As explained above, a correlation signal that shows a more certaintiming phase is selected based on a simple calculation shown in theequations (33a), (33b), (34a), (34b), (35a), and (35b), regardless ofvector angle θW_(i). Further, the doubling processing of the phase iscarried out based on the equation (15) after the averaging, not beforethe averaging like the seventh embodiment and the eighth embodiment.Therefore, it is possible to realize the timing phase detection inhigher precision than that in the seventh embodiment and the eighthembodiment. At the same time, it is possible to reduce the processingvolume.

Further, like in the seventh embodiment, the timing regenerating devicehaving the averaging unit in the ninth embodiment shown in FIG. 18 cancarry out the estimation of a timing phase and the detection of apreamble at high precision regardless of a carrier phase, when thepreamble symbol is a signal that alternately shifts between two pointsfor each one symbol on a complex plane, like the preamble symbol thatalternately shifts between two adjacent Nyquist points for each symbolon the complex plane as shown in FIG. 35, in addition to the preamblesymbol that alternately shifts between two Nyquist points for eachsymbol that become symmetrical with the origin (that shifts ±180 [deg]for each symbol) on the complex plane as shown in FIG. 22.

FIG. 19 is a structure diagram of a demodulator according to a tenthembodiment of the present invention. This demodulator is such that, likethe demodulator in the seventh embodiment shown in FIG. 16, during thereception of a random pattern, the timing phase is traced based on theconventional PLL, and at the same time, the influence of theover-amplification due the AGC is avoided. Sections identical to orcorresponding to those of the demodulator shown in FIG. 14 and FIG. 16are attached with the same reference numbers.

This demodulator comprises the phase detecting unit 424, averaging unit425, preamble detecting/timing phase difference calculating unit 423 a,VCO 401 a, and clip detecting unit 440.

Operation of the demodulator according to the tenth embodiment will nowbe explained. The antenna 100 receives a burst signal of an RF band. Thefrequency converting unit 200, first A/D converter 301 a, and second A/Dconverter 301 b carry out the processing as explained above. The firstA/D converter 301 a outputs a sampled received data string I_(i) (i=1,2, 3, . . . ), and the second A/D converter 301 b outputs a sampledreceived data string Q_(i) (i=1, 2, 3, . . . ).

The clip detecting unit 440 receives the data strings I_(i) (i=1, 2, 3,. . . ) and Q_(i) (i=1, 2, 3, . . . ), and detects an output value. Theclip detecting unit 440 decides whether this output value is within apredetermined permissible range. When this output value exceeds thepermissible range or is lower than the permissible range, the clipdetecting unit 440 decides that an over-amplified signal that exceedsthe input range of the A/D converters has been input into the A/Dconverters due to the operation of the AGC. Then, the clip detectingunit 440 converts the output values of both the first A/D converter 301a and second A/D converter 301 b to “0”, and outputs the value toin-phase component square calculation unit 420 a and orthogonalcomponent square calculation unit 420 b provided at the latter stage.When the output value is within the permissible range, the output valueis output as it is.

Subsequently, the sections from the in-phase component squarecalculation unit 420 a and orthogonal component square calculation unit420 b up to the preamble detecting/timing phase difference calculatingunit 423 a perform the processing as explained above, and a phasecontrol signal for canceling a timing error τ is output.

In the absence of the clip detecting unit 440, a preamble symbol that isoriginally a sinusoidal wave is distorted into a rectangular wave and isinput into a circuit at the latter stage, when an over-amplificationthat exceeds the input range of each A/D converter has occurred due tothe operation of the AGC. This degrades the precision in the estimate ofthe timing phase. On the other hand, when the clip detecting unit 440 isprovided, the over-amplification is detected even when theover-amplification that exceeds the input range of each A/D converterhas occurred due to the operation of the AGC. Thus, the received signalat this time is made invalid (converted to “0”). Therefore, the timingregenerating device 400 does not carry out the estimation of a timingphase that uses the preamble symbol distorted into the rectangularshape. The timing regenerating device 400 can start the operation afterleading the AGC when the input level has entered within the input rangeof each A/D converter. As a result, the timing regenerating device 400can avoid the degradation in the precision of estimating the timingphase at the AGC leading time.

During the reception of the preamble symbol and after completing theleading of the AGC, the vector length V_(i) of the timing regeneratingdevice 400 has a constant and large value and the timing phasedifference θs [deg] becomes a certain value, regardless of the carrierphase θc, like in the fourth embodiment.

On the other hand, during the reception when there is no signal(receiving only noise in the absence of a signal) or during thereception of a significant data section that follows the preamble, orduring the process of leading the AGC, the vector length V_(i) has asmaller value, and the timing phase difference θr_(i) [deg] becomes anuncertain value.

Therefore, when the reception timing of the burst signal is not knownand also when the arrival time of the preamble symbol is not known, thepreamble detecting/timing phase difference calculating unit 423 a canobtain the timing error τ.

When a vector length V_(i) is large as a result of monitoring V_(i) (forexample, when the vector length V_(i) exceeds a certain threshold valueεp), a decision is made as “preamble is being received after completingthe leading of the AGC”, and the timing phase difference θr_(i) [deg] islatched at the timing shown in FIG. 5. As is clear from FIG. 5, thelatched timing phase difference θr_(i) [deg] is a timing phasedifference θr_(i) [deg] when V_(i) is large. Therefore, this is acertain value. The preamble detecting/timing phase differencecalculating unit 423 a obtains the timing error τ from the equations(16a) and (16b) using the timing phase difference θs obtained from theabove processing, and gives a phase control signal for canceling thetiming error τ to the VCO 401 a at the latter stage.

In the mean time, the phase detecting unit 424 detects whether a timingphase is advanced or delayed from received data (I_(i), Q_(i)). When thetiming phase is advanced, “+1” is output, and when the timing phase isdelayed, “−1” is output.

The averaging unit 425 calculates an average of the detection signalsthat show this advance/delay using a random work filter, for example,and outputs the average as a phase advance/delay signal.

The VCO 401 a controls the phases of a regeneration sample clock and aregeneration symbol clock based on the phase advance/delay signal. Whenthis phase advance/delay signal is “positive”, the VCO 401 a advancesthe timing phase, and when the phase advance/delay signal is “negative”,the VCO 401 a delays the timing phase. The VCO 401 a is usuallycontrolled based on the phase advance/delay signal. However, when apreamble has been detected and also when a phase control signal has beeninput, the VCO 401 a controls each clock phase by using the phasecontrol signal without using the phase advance/delay signal.

As explained above, the clip detecting unit 440 reduces the increase intiming error due to the AGC leading operation, and the PLL type is usedat the same time. Based on this arrangement, it is possible to realizethe tracing of the timing phase during the reception of the significantrandom data while carrying out the estimating and control of the timingphase at high precision using a short preamble symbol.

Further, when the AGC (Automatic Gain Control) is used for controllingthe level of the reception signal, it is possible to carry out thetiming regeneration at high precision without an increase in the errorof estimating the timing phase, when the reception signal over-amplifiedby the AGC has been input.

Use of the clip detecting unit 440 is not limited to the tenthembodiment. For example, it is of course possible to use the clipdetecting unit 440 for the timing regenerating device described in thefirst to eighth embodiments. The received data string I_(i) (i=1, 2, 3,. . . ) and the received data string Q_(i) (i=1, 2, 3, . . . ) outputfrom this clip detecting unit 440 may be input into the in-phasecomponent square calculation unit 420 a and orthogonal component squarecalculation unit 420 b provided at the latter stage respectively.

Further, like in the first embodiment, the timing regenerating devicehaving the averaging unit in the tenth embodiment can carry out theestimation of a timing phase and the detection of a preamble at highprecision regardless of a carrier phase, when the preamble symbol is asignal that alternately shifts between two points for each one symbol ona complex plane, like the preamble symbol that alternately shiftsbetween two adjacent Nyquist points for each symbol on the complex planeas shown in FIG. 35, in addition to the preamble symbol that alternatelyshifts between two Nyquist points for each symbol that becomesymmetrical with the origin (that shifts ±180 [deg] for each symbol) onthe complex plane as shown in FIG. 22.

As explained above, according to the present invention, it is possibleto realize the estimation of a timing phase at high precision withoutreceiving an influence of the carrier phase θc. Further, it is possibleto normally carry out the timing phase control. Further, it is possibleto realize satisfactory BER characteristics at the power supply start-uptime or at the line reconnection time after recovery from a shadowing isunknown, it is not possible to know the reception timing of a preamblesymbol.

Industrial Applicability

As explained above, the timing regenerating device and the demodulatorrelating to the present invention can be applied to a broad-band digitalradio communication system having a preamble symbol at the header of theburst signal. They are suitable for calculating a timing error at highprecision without receiving an influence of the carrier phase θc.

What is claimed is:
 1. A timing regenerating device comprising: anin-phase component square calculation unit that receives a base bandsignal having a preamble symbol, calculates square of an in-phasecomponent of the base band signal and outputs the squared in-phasecomponent; an in-phase multiplier that multiplies a sign bit (±1) of thein-phase component of the base band signal to the squared in-phasecomponent and outputs the result as signed squared in-phase component;an orthogonal component square calculation unit that receives the baseband signal, calculates square of an orthogonal component of the baseband signal and outputs the squared orthogonal component; an orthogonalmultiplier that multiplies a sign bit (±1) of the orthogonal componentof the base band signal to the squared orthogonal component and outputsthe result as a signed squared orthogonal component; a squared-preamblein-phase correlation calculating unit that calculates a correlationvalue between the signed squared in-phase component and a ½ symbolfrequency component, and outputs the correlation value as an in-phasecorrelation signal; a squared-preamble orthogonal correlationcalculating unit that calculates a correlation value between the signedsquared orthogonal component and the ½ symbol frequency component, andoutputs the correlation value as an orthogonal correlation signal; avector combination selecting unit that compares the magnitudes of thein-phase and orthogonal correlation signals, matches the direction of avector obtained from the in-phase or orthogonal correlation signalswhichever is smaller to the direction of a vector obtained from thein-phase or orthogonal correlation signals whichever is larger, combinesthese signals, and outputs a correlation signal after the combination asa combined correlation signal; and a timing phase difference calculatingunit that outputs a phase control signal based on a vector angle shownby the combined correlation signal.
 2. A timing regenerating deviceaccording to claim 1, further comprising: a VCO that outputs aregeneration symbol clock, a regeneration sample clock, and the ½ symbolfrequency component, based on the phase control signal, wherein the baseband signal to be input into the in-phase component square calculationunit and the orthogonal component square calculation unit is a signalthat has been sampled based on the regeneration sample clock, saidsquared-preamble in-phase correlation calculating unit calculates thecorrelation value using the ½ symbol frequency component output fromsaid VCO, and said squared-preamble orthogonal correlation calculatingunit calculates the correlation value using the ½ symbol frequencycomponent output from said VCO.
 3. A timing regenerating deviceaccording to claim 2, further comprising: a phase detecting unit thatdetects advancement/delay of a timing phase using the base band signalsampled based on the regeneration sample clock, and outputs detectedsignals as phase detection signals; and a phase detection signalaveraging unit that calculates an average of the phase detectionsignals, and outputs the average as a phase advance/delay signal,wherein said VCO outputs the regeneration symbol clock, the regenerationsample clock, and the ½ symbol frequency component, based on the phasecontrol signal and the phase advance/delay signal.
 4. A timingregenerating device according to claim 1, further comprising: anoscillator that outputs an asynchronous sample clock and the ½ symbolfrequency component, wherein the base band signal to be input into saidin-phase component square calculation unit and said orthogonal componentsquare calculation unit is a signal that has been sampled based on theasynchronous sample clock, said squared-preamble in-phase correlationcalculating unit calculates the correlation value using the ½ symbolfrequency component output from said oscillator, and saidsquared-preamble orthogonal correlation calculating unit calculates thecorrelation value using the ½ symbol frequency component output fromsaid oscillator.
 5. A timing regenerating device according to claim 1,wherein said timing phase difference calculating unit calculates atiming phase difference from a square root of the in-phase component andthe vector angle of a square root of the orthogonal component of thecombined correlation signal.
 6. A timing regenerating device accordingto claim 1, further comprising: a clip detecting unit configured toreceive digitally sampled in-phase and quadrature components of the baseband signal having a preamble symbol, and either converts both thein-phase and orthogonal components of the base band signal into “0” whenat least one value of the in-phase and orthogonal components of the baseband signal is outside a predetermined range or outputs the received,digitally sampled in-phase and quadrature components of the base bandsignal without alteration when all values of the in-phase and orthogonalcomponents of the base band signal are within the predetermined range,wherein the base band signal to be input into said in-phase componentsquare calculation unit and into said orthogonal component squarecalculation unit is the base band signal output of said clip detectingunit.
 7. A timing regenerating device comprising: an in-phase componentsquare calculation unit that receives a base band signal having apreamble symbol, calculates square of an in-phase component of the baseband signal and outputs the squared in-phase component; an in-phasemultiplier that multiplies a sign bit (±1) of the in-phase component ofthe base band signal to the squared in-phase component and outputs theresult as signed squared in-phase component; an orthogonal componentsquare calculation unit that receives the base band signal, calculatessquare of an orthogonal component of the base band signal and outputsthe squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; a squared-preamble in-phasecorrelation calculating unit that calculates a correlation value betweenthe signed squared in-phase component and a ½ symbol frequencycomponent, and outputs the correlation value as an in-phase correlationsignal; a squared-preamble orthogonal correlation calculating unit thatcalculates a correlation value between the signed squared orthogonalcomponent and the ½ symbol frequency component, and outputs thecorrelation value as an orthogonal correlation signal; a vectorcombination selecting unit that compares the magnitudes of the in-phaseand orthogonal correlation signals, matches the direction of a vectorobtained from the in-phase or orthogonal correlation signals whicheveris smaller to the direction of a vector obtained from the in-phase ororthogonal correlation signals whichever is larger, combines thesesignals, and outputs a correlation signal after the combination as acombined correlation signal; and a preamble detecting/timing phasedifference calculating unit that calculates a vector angle and a vectorlength of the combined correlation signal, decides that the preamblesymbol has been detected when the vector length is larger than apredetermined threshold value, calculates a timing phase differenceusing a vector angle shown by the combined correlation signal at thattime, and outputs a phase control signal.
 8. A timing regeneratingdevice according to claim 7, further comprising: a VCO that outputs aregeneration symbol clock, a regeneration sample clock, and the ½ symbolfrequency component, based on the phase control signal, wherein the baseband signal to be input into the in-phase component square calculationunit and the orthogonal component square calculation unit is a signalthat has been sampled based on the regeneration sample clock, saidsquared-preamble in-phase correlation calculating unit calculates thecorrelation value using the ½ symbol frequency component output fromsaid VCO, and said squared-preamble orthogonal correlation calculatingunit calculates correlation value using the ½ symbol frequency componentoutput from said VCO.
 9. A timing regenerating device according to claim8, further comprising: a phase detecting unit that detectsadvancement/delay of a timing phase using the base band signal sampledbased on the regeneration sample clock, and outputs detected signals asphase detection signals; and a phase detection signal averaging unitthat calculates an average of the phase detection signals, and outputsthe average as a phase advance/delay signal, wherein said VCO outputsthe regeneration symbol clock, the regeneration sample clock, and the ½symbol frequency component, based on the phase control signal and thephase advance/delay signal.
 10. A timing regenerating device accordingto claim 7, further comprising: an oscillator that outputs anasynchronous sample clock and the ½ symbol frequency component, whereinthe base band signal to be input into said in-phase component squarecalculation unit and said orthogonal component square calculation unitis a signal that has been sampled based on the asynchronous sampleclock, said squared-preamble in-phase correlation calculating unitcalculates the correlation value using the ½ symbol frequency componentoutput from said oscillator, and said squared-preamble orthogonalcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said oscillator.
 11. A timingregenerating device according to claim 7, wherein said preambledetecting/timing phase difference calculating unit calculates a timingphase difference from a vector angle shown by a value obtained bymultiplying a sign {±1} of the in-phase component to a square root of anabsolute value of an in-phase component of a combined correlation signaland a value obtained by multiplying a sign {±1} of the orthogonalcomponent to a square root of an absolute value of an orthogonalcomponent of the combined correlation signal.
 12. A timing regeneratingdevice according to claim 7, further comprising: a clip detecting unitconfigured to receive digitally sampled in-phase and quadraturecomponents of the base band signal having a preamble symbol, and eitherconverts both the in-phase and orthogonal components of the base bandsignal into “0” when at least one value of the in-phase and orthogonalcomponents of the base band signal is outside a predetermined range oroutputs the received, digitally sampled in-phase and quadraturecomnponents of the base band signal without alteration when all valuesof the in-phase and orthogonal components of the base band signal arewithin the predetermined range, wherein the base band signal to be inputinto said in-phase component square calculation unit and into saidorthogonal component square calculation unit is the base band signaloutput of said clip detecting unit.
 13. A timing regenerating devicecomprising: an in-phase component square calculation unit that receivesa base band signal having a preamble symbol, calculates square of anin-phase component of the base band signal and outputs the squaredin-phase component; an in-phase multiplier that multiplies a sign bit(±1) of the in-phase component of the base band signal to the squaredin-phase component and outputs the result as signed squared in-phasecomponent; an orthogonal component square calculation unit that receivesthe base band signal, calculates square of an orthogonal component ofthe base band signal and outputs the squared orthogonal component; anorthogonal multiplier that multiplies a sign bit (±1) of the orthogonalcomponent of the base band signal to the squared orthogonal componentand outputs the result as a signed squared orthogonal component; anadder that adds the signed squared in-phase and orthogonal components togenerate a squared addition signal, and outputs the squared additionsignal; a subtracter that subtracts the signed squared in-phasecomponent from the signed squared orthogonal component or vice versa togenerate a squared subtraction signal, and outputs the squaredsubtraction signal; a squared-addition signal component correlationcalculating unit that calculates a correlation value between the squaredaddition signal and a ½ symbol frequency component, and outputs thiscorrelation value as an addition correlation signal; asquared-subtraction signal component correlation calculating unit thatcalculates a correlation value between the squared subtraction signaland the ½ symbol frequency component, and outputs this correlation valueas a subtraction correlation signal; a vector selecting unit thatcompares the magnitudes of the addition and subtraction correlationsignals, selects the addition correlation signal or the subtractioncorrelation signal whichever is larger, and outputs this signal as aselected correlation signal; and a timing phase difference calculatingunit that outputs a phase control signal based on a vector angle shownby the selected correlation signal.
 14. A timing regenerating deviceaccording to claim 13, further comprising: a VCO that outputs aregeneration symbol clock, a regeneration sample clock, and the ½ symbolfrequency component, based on the phase control signal, wherein the baseband signal to be input into the in-phase component square calculationunit and the orthogonal component square calculation unit is a signalthat has been sampled based on the regeneration sample clock, saidsquared-addition signal component correlation calculating unitcalculates the correlation value using the ½ symbol frequency componentoutput from said VCO, and said squared-subtraction signal componentcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said VCO.
 15. A timingregenerating device according to claim 14, further comprising: a phasedetecting unit that detects advancement/delay of a timing phase usingthe base band signal sampled based on the regeneration sample clock, andoutputs detected signals as phase detection signals; and a phasedetection signal averaging unit that calculates an average of the phasedetection signals, and outputs the average as a phase advance/delaysignal, wherein said VCO outputs the regeneration symbol clock, theregeneration sample clock, and the ½ symbol frequency component, basedon the phase control signal and the phase advance/delay signal.
 16. Atiming regenerating device according to claim 13, further comprising: anoscillator that outputs an asynchronous sample clock and the ½ symbolfrequency component, wherein the base band signal to be input into saidin-phase component square calculation unit and said orthogonal componentsquare calculation unit is a signal that has been sampled based on theasynchronous sample clock, said squared-addition signal componentcorrelation calculating unit calculates correlation value using the ½symbol frequency component output from said oscillator, and saidsquared-subtraction signal component correlation calculating unitcalculates correlation value using the ½ symbol frequency componentoutput from said oscillator.
 17. A timing regenerating device accordingto claim 13, wherein said adder adds the signed squared in-phase andorthogonal components to obtain a result as a squared addition signal,and the subtracter subtracts the signed squared in-phase component fromthe signed squared orthogonal component or vice versa, and obtains aresult as a squared subtraction signal.
 18. A timing regenerating deviceaccording to claim 13, wherein said adder adds the signed squaredin-phase and orthogonal components and, multiplies a sign {±1} of thissum to a square root of an absolute value of the sum, thereby to obtaina squared addition signal, and the subtracter subtracts the signedsquared in-phase component from the signed squared orthogonal componentor vice versa, and multiplies a sign {±1} of this difference to a squareroot of an absolute value of the difference, thereby to obtain a squaredsubtraction signal.
 19. A timing regenerating device according to claim13, further comprising: a clip detecting unit configured to receivedigitally sampled in-phase and quadrature components of the base bandsignal having the preamble symbol, and either converts both the in-phaseand orthogonal components of the base band signal into “0” when at leastone value of the in-phase and orthogonal components of the base bandsignal is outside a predetermined range or outputs the received,digitally sampled in-phase and quadrature components of the base bandsignal without alteration when all values of the in-phase and orthogonalcomponents of the base band signal are within the predetermined range,wherein the base band signal to be input into said in-phase componentsquare calculation unit and into said orthogonal component squarecalculation unit is the base band signal output of said clip detectingunit.
 20. A timing regenerating device comprising: an in-phase componentsquare calculation unit that receives a base band signal having apreamble symbol, calculates square of an in-phase component of the baseband signal and outputs the squared in-phase component; an in-phasemultiplier that multiplies a sign bit (±1) of the in-phase component ofthe base band signal to the squared in-phase component and outputs theresult as signed squared in-phase component; an orthogonal componentsquare calculation unit that receives the base band signal, calculatessquare of an orthogonal component of the base band signal and outputsthe squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; an adder that adds the signedsquared in-phase and orthogonal components and generates a squaredaddition signal, and outputs the squared addition signal; a subtracterthat subtracts the signed squared in-phase component from the signedsquared orthogonal component or vice versa and generates a squaredsubtraction signal, and outputs the squared subtraction signal; asquared-addition signal component correlation calculating unit thatcalculates a correlation value between the squared addition signal and a½ symbol frequency component, and outputs this correlation value as anaddition correlation signal; a squared-subtraction signal componentcorrelation calculating unit that calculates a correlation value betweenthe squared subtraction signal and the ½ symbol frequency component, andoutputs this correlation value as a subtraction correlation signal; avector selecting unit that compares the magnitude of the additioncorrelation signal with the magnitude of the subtraction correlationsignal, selects the addition correlation signal or the subtractioncorrelation signal whichever is larger, and outputs this signal as aselected correlation signal; and a preamble detecting/timing phasedifference calculating unit that calculates a vector angle and a vectorlength of the selected correlation signal, decides that the preamblesymbol has been detected when the vector length is larger than apredetermined threshold value, calculates a timing phase differenceusing a vector angle shown by the selected correlation signal at thattime, and outputs a phase control signal.
 21. A timing regeneratingdevice according to claim 20, further comprising: a VCO that outputs aregeneration symbol clock, a regeneration sample clock, and the ½ symbolfrequency component, based on the phase control signal, wherein the baseband signal to be input into said in-phase component square calculationunit and said orthogonal component square calculation unit is a signalthat has been sampled based on the regeneration sample clock, saidsquared-addition signal component correlation calculating unitcalculates the correlation value using the ½ symbol frequency componentoutput from said VCO, and said squared-subtraction signal componentcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said VCO.
 22. A timingregenerating device according to claim 21, further comprising: a phasedetecting unit that detects advancement/delay of a timing phase usingthe base band signal sampled based on the regeneration sample clock, andoutputs detected signals as phase detection signals; and a phasedetection signal averaging unit that calculates an average of the phasedetection signals, and outputs the average as a phase advance/delaysignal, wherein said VCO outputs the regeneration symbol clock, theregeneration sample clock, and the ½ symbol frequency component, basedon both the phase control signal and the phase advance/delay signal. 23.A timing regenerating device according to claim 20, further comprising:an oscillator that outputs an asynchronous sample clock and the ½ symbolfrequency component, wherein the base band signal to be input into saidin-phase component square calculation unit and said orthogonal componentsquare calculation unit is a signal that has been sampled based on theasynchronous sample clock, said squared-addition signal componentcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said oscillator, and saidsquared-subtraction signal component correlation calculating unitcalculates the correlation value using the ½ symbol frequency componentoutput from said oscillator.
 24. A timing regenerating device accordingto claim 20, wherein said adder adds the signed squared in-phase andorthogonal components to obtain the squared addition signal, and thesubtracter subtracts the signed squared in-phase component from thesigned squared orthogonal component or vice versa to obtain the squaredsubtraction signal.
 25. A timing regenerating device according to claim20, wherein said adder adds the signed squared in-phase and orthogonalcomponents, multiplies a sign {±1} of this sum to a square root of anabsolute value of the sum, thereby to obtain the squared additionsignal, and the subtracter subtracts the signed squared in-phasecomponent from the signed squared orthogonal component or vice versa,multiplies a sign {±1} of this difference to a square root of anabsolute value of the difference, thereby to obtain the squaredsubtraction signal.
 26. A timing regenerating device according to claim20, further comprising: a clip detecting unit configured to receivedigitally sampled in-phase and quadrature components of the base bandsignal having the preamble symbol, and either converts both the in-phaseand orthogonal components of the base band signal into “0” when at leastone value of the in-phase and orthogonal components of the base bandsignal is outside a predetermined range or outputs the received,digitally sampled in-phase and quadrature components of the base bandsignal without alterations when all values of the in-phase andorthogonal components of the base band signal are within thepredetermined range, wherein the base band signal to be input into saidin-phase component square calculation unit and into said orthogonalcomponent square calculation unit is the base band signal output of saidclip detecting unit.
 27. A timing regenerating device comprising: anin-phase component square calculation unit that receives a base bandsignal having a preamble symbol, calculates square of an in-phasecomponent of the base band signal and outputs the squared in-phasecomponent; an in-phase multiplier that multiplies a sign bit (±1) of thein-phase component of the base band signal to the squared in-phasecomponent and outputs the result as signed squared in-phase component;an orthogonal component square calculation unit that receives the baseband signal, calculates square of an orthogonal component of the baseband signal and outputs the squared orthogonal component; an orthogonalmultiplier that multiplies a sign bit (±1) of the orthogonal componentof the base band signal to the squared orthogonal component and outputsthe result as a signed squared orthogonal component; an adder that addsthe signed squared in-phase and orthogonal components to obtain asquared addition signal, and outputs the squared addition signal; asubtracter that subtracts the signed squared in-phase component from thesigned squared orthogonal component or vice versa to obtain a squaredsubtraction signal, and outputs the squared subtraction signal; asquared-addition signal component correlation calculating unit thatcalculates a correlation value between the squared addition signal and a½ symbol frequency component, and outputs this correlation value as anaddition correlation signal; a squared-subtraction signal componentcorrelation calculating unit that calculates a correlation value betweenthe squared subtraction signal and the ½ symbol frequency component, andoutputs this correlation value as a subtraction correlation signal; avector selecting unit that compares the magnitudes of the addition andsubtraction correlation signals, selects the addition correlation signalor the subtraction correlation signal whichever is larger, and outputsthis signal as a selected correlation signal; a weighting unit thatgives a weight corresponding to a vector length shown by the selectedcorrelation signal to the selected correlation signal, and outputs theweighted correlation signal; an averaging unit that doubles the weightedcorrelation, calculates an average of the signals, and outputs thisaverage as a weighted average correlation signal; and a timing phasedifference calculating unit that outputs a phase control signal based ona vector angle shown by the weighted average correlation signal.
 28. Atiming regenerating device according to claim 27, further comprising: aVCO that outputs a regeneration symbol clock, a regeneration sampleclock, and the ½ symbol frequency component, based on the phase controlsignal, wherein the base band signal to be input into said in-phasecomponent square calculation unit and said orthogonal component squarecalculation unit is a signal that has been sampled based on theregeneration sample clock, said squared-addition signal componentcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said VCO, and saidsquared-subtraction signal component correlation calculating unitcalculates correlation value using the ½ symbol frequency componentoutput from said VCO.
 29. A timing regenerating device according toclaim 27, further comprising: an oscillator that outputs an asynchronoussample clock and the ½ symbol frequency component, wherein the base bandsignal to be input into said in-phase component square calculation unitand said orthogonal component square calculation unit is a signal thathas been sampled by the asynchronous sample clock, said squared-additionsignal component correlation calculating unit calculates the correlationvalue using the ½ symbol frequency component output from saidoscillator, and said squared-subtraction signal component correlationcalculating unit calculates the correlation value using the ½ symbolfrequency component output from said oscillator.
 30. A timingregenerating device according to claim 27, wherein said adder adds thesigned squared in-phase and orthogonal components to obtain the squaredaddition signal, and the subtracter subtracts the signed squaredin-phase component from the signed squared orthogonal component or viceversa to obtain the squared subtraction signal.
 31. A timingregenerating device according to claim 27, wherein said adder adds thesigned squared in-phase and orthogonal components and, multiplies a sign{±1} of this sum to a square root of an absolute value of the sum,thereby to obtain the squared addition signal, and the subtractersubtracts the signed squared in-phase component from the signed squaredorthogonal component or vice versa, and multiplies a sign {±1} of thisdifference to a square root of an absolute value of the difference,thereby to obtain the squared subtraction signal.
 32. A timingregenerating device according to claim 27, wherein when the in-phasecomponent of a weighted correlation signal is negative, said averagingunit inverts the signs of the in-phase and orthogonal components of theweighted correlation signal respectively, and generates a correlationsignal with the inverted signs as a first correlation signal, when thein-phase component of the weighted correlation signal is positive, saidaveraging unit generates this weighted correlation signal as a firstcorrelation signal, when the orthogonal component of the weightedcorrelation signal is negative, said averaging unit inverts the signs ofthe in-phase and orthogonal components of the weighted correlationsignal respectively, and generates a correlation signal with theinverted signs as a second correlation signal, when the orthogonalcomponent of the weighted correlation signal is positive, said averagingunit generates this weighted correlation signal as a second correlationsignal, and said averaging unit calculates averages of the first andsecond correlation signals respectively, and when the vector length ofthe averaged first correlation signal is larger than the vector lengthof the averaged second correlation signal, said averaging unit outputsthe averaged first correlation signal as the weighted averagecorrelation signal, and when the vector length of the averaged secondcorrelation signal is larger than the vector length of the averagedfirst correlation signal, said averaging unit outputs the averagedsecond correlation signal as the weighted average correlation signal.33. A timing regenerating device according to claim 27, furthercomprising: a clip detecting unit configured to receive digitallysampled in-phase and quadrature components of the base band signalhaving the preamble symbol, and either converts both the in-phase andorthogonal components of the base band signal into “0” when at least onevalue of the in-phase and orthogonal components of the base band signalis outside a predetermined range or outputs the received, digitallysampled in-phase and quadrature comnponents of the base band signalstraight when at least one value of the in-phase and orthogonalcomponents of the base band signal are within the predetermined range,wherein the base band signal input into said in-phase component squarecalculation unit and into said orthogonal component square calculationunit is the base band signal output of said clip detecting unit.
 34. Ademodulator comprising: an antenna that receives a radio signal; afrequency converting unit that converts the frequency of the receivedradio signal into the frequency of a base band signal; an A/D convertingunit that converts the base band signal into a digital base band signalbased on a sampling at two times a symbol rate using a regenerationsample clock; a timing regenerating device including: an in-phasecomponent square calculation unit that receives a base band signalhaving a preamble symbol, calculates square of an in-phase component ofthe base band signal and outputs the squared in-phase component; anin-phase multiplier that multiplies a sign bit (±1) of the in-phasecomponent of the base band signal to the squared in-phase component andoutputs the result as signed squared in-phase component; an orthogonalcomponent square calculation unit that receives the base band signal,calculates square of an orthogonal component of the base band signal andoutputs the squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; a squared-preamble in-phasecorrelation calculating unit that calculates a correlation value betweenthe signed squared in-phase component and a ½ symbol frequencycomponent, and outputs the correlation value as an in-phase correlationsignal; a squared-preamble orthogonal correlation calculating unit thatcalculates a correlation value between the signed squared orthogonalcomponent and the ½ symbol frequency component, and outputs thecorrelation value as an orthogonal correlation signal; a vectorcombination selecting unit that compares the magnitudes of the in-phaseand orthogonal correlation signals, matches the direction of a vectorobtained from the in-phase or orthogonal correlation signals whicheveris smaller to the direction of a vector obtained from the in-phase ororthogonal correlation signals whichever is larger, combines thesesignals, and outputs a correlation signal after the combination as acombined correlation signal; a timing phase difference calculating unitthat outputs a phase control signal from a vector angle shown by thecombined correlation signal; a VCO that outputs a regeneration symbolclock, a regeneration sample clock, and the ½ symbol frequencycomponent, based on the phase control signal, wherein the base bandsignal to be input into the in-phase component square calculation unitand the orthogonal component square calculation unit is a signal thathas been sampled based on the regeneration sample clock, saidsquared-preamble in-phase correlation calculating unit calculates thecorrelation value using the ½ symbol frequency component output fromsaid VCO, and said squared-preamble orthogonal correlation calculatingunit calculates the correlation value using the ½ symbol frequencycomponent output from said VCO; a phase detecting unit that detectsadvancement/delay of a timing phase using the base band signal sampledbased on the regeneration sample clock, and outputs detected signals asphase detection signals; a phase detection signal averaging unit thatcalculates an average of the phase detection signals, and outputs theaverage as a phase advance/delay signal, wherein said VCO outputs theregeneration symbol clock, the regeneration sample clock, and the ½symbol frequency component, based on the phase control signal and thephase advance/delay signal; and a data deciding unit that extractsNyquist point data from the digital base band signal using theregeneration symbol clock, decides the extracted Nyquist point data, andoutputs the data as demodulated data.
 35. A demodulator comprising: anantenna that receives a radio signal; a frequency converting unit thatconverts the frequency of the received radio signal into the frequencyof a base band signal; an A/D converting unit that converts the baseband signal into a digital base band signal based on a sampling at twotimes a symbol rate using a regeneration sample clock; a timingregenerating device including: an in-phase component square calculationunit that receives a base band signal having a preamble symbol,calculates square of an in-phase component of the base band signal andoutputs the squared in-phase component; an in-phase multiplier thatmultiplies a sign bit (±1) of the in-phase component of the base bandsignal to the squared in-phase component and outputs the result assigned squared in-phase component; an orthogonal component squarecalculation unit that receives the base band signal, calculates squareof an orthogonal component of the base band signal and outputs thesquared orthogonal component; an orthogonal multiplier that multiplies asign bit (±1) of the orthogonal component of the base band signal to thesquared orthogonal component and outputs the result as a signed squaredorthogonal component; a squared-preamble in-phase correlationcalculating unit that calculates a correlation value between the signedsquared in-phase component and a ½ symbol frequency component, andoutputs the correlation value as an in-phase correlation signal; asquared-preamble orthogonal correlation calculating unit that calculatesa correlation value between the signed squared orthogonal component andthe ½ symbol frequency component, and outputs the correlation value asan orthogonal correlation signal; a vector combination selecting unitthat compares the magnitudes of the in-phase and orthogonal correlationsignals, matches the direction of a vector obtained from the in-phase ororthogonal correlation signals whichever is smaller to the direction ofa vector obtained from the in-phase or orthogonal correlation signalswhichever is larger, combines these signals, and outputs a correlationsignal after the combination as a combined correlation signal; a timingphase difference calculating unit that outputs a phase control signalfrom a vector angle shown by the combined correlation signal; anoscillator that outputs an asynchronous sample clock and the ½ symbolfrequency component, wherein the base band signal to be input into saidin-phase component square calculation unit and said orthogonal componentsquare calculation unit is a signal that has been sampled based on theasynchronous sample clock, said squared-preamble in-phase correlationcalculating unit calculates the correlation value using the ½ symbolfrequency component output from said oscillator, said squared-preambleorthogonal correlation calculating unit calculates the correlation valueusing the ½ symbol frequency component output from said oscillator; anda data deciding unit that extracts Nyquist point data from the digitalbase band signal using the regeneration symbol clock, decides theextracted Nyquist point data, and outputs the data as demodulated data.36. A demodulator comprising: an antenna that receives a radio signal; afrequency converting unit that converts the frequency of the receivedradio signal into the frequency of a base band signal; an A/D convertingunit that converts the base band signal into a digital base band signalbased on a sampling at two times a symbol rate using a regenerationsample clock; a timing regenerating device including: an in-phasecomponent square calculation unit that receives a base band signalhaving a preamble symbol, calculates square of an in-phase component ofthe base band signal and outputs the squared in-phase component; anin-phase multiplier that multiplies a sign bit (±1) of the in-phasecomponent of the base band signal to the squared in-phase component andoutputs the result as signed squared in-phase component; an orthogonalcomponent square calculation unit that receives the base band signal,calculates square of an orthogonal component of the base band signal andoutputs the squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; a squared-preamble in-phasecorrelation calculating unit that calculates a correlation value betweenthe signed squared in-phase component and a ½ symbol frequencycomponent, and outputs the correlation value as an in-phase correlationsignal; a squared-preamble orthogonal correlation calculating unit thatcalculates a correlation value between the signed squared orthogonalcomponent and the ½ symbol frequency component, and outputs thecorrelation value as an orthogonal correlation signal; a vectorcombination selecting unit that compares the magnitudes of the in-phaseand orthogonal correlation signals, matches the direction of a vectorobtained from the in-phase or orthogonal correlation signals whicheveris smaller to the direction of a vector obtained from the in-phase ororthogonal correlation signals whichever is larger, combines thesesignals, and outputs a correlation signal after the combination as acombined correlation signal; a preamble detecting/timing phasedifference calculating unit that calculates a vector angle and a vectorlength of the combined correlation signal, decides that the preamblesymbol has been detected when the vector length is larger than apredetermined threshold value, calculates a timing phase differenceusing a vector angle shown by the combined correlation signal at thattime, and outputs a phase control signal; an oscillator that outputs anasynchronous sample clock and the ½ symbol frequency component, whereinthe base band signal to be input into said in-phase component squarecalculation unit and said orthogonal component square calculation unitis a signal that has been sampled based on the asynchronous sampleclock, said squared-preamble in-phase correlation calculating unitcalculates the correlation value using the ½ symbol frequency componentoutput from said oscillator, said squared-preamble orthogonalcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said oscillator; and a datadeciding unit that extracts Nyquist point data from the digital baseband signal using the regeneration symbol clock, decides the extractedNyquist point data, and outputs the data as demodulated data.
 37. Ademodulator comprising: an antenna that receives a radio signal; afrequency converting unit that converts the frequency of the receivedradio signal into the frequency of a base band signal; an A/D convertingunit that converts the base band signal into a digital base band signalbased on a sampling at two times a symbol rate using a regenerationsample clock; a timing regenerating device including: an in-phasecomponent square calculation unit that receives a base band signalhaving a preamble symbol, calculates square of an in-phase component ofthe base band signal and outputs the squared in-phase component; anin-phase multiplier that multiplies a sign bit (±1) of the in-phasecomponent of the base band signal to the squared in-phase component andoutputs the result as signed squared in-phase component; an orthogonalcomponent square calculation unit that receives the base band signal,calculates square of an orthogonal component of the base band signal andoutputs the squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; a squared-preamble in-phasecorrelation calculating unit that calculates a correlation value betweenthe signed squared in-phase component and a ½ symbol frequencycomponent, and outputs the correlation value as an in-phase correlationsignal; a squared-preamble orthogonal correlation calculating unit thatcalculates a correlation value between the signed squared orthogonalcomponent and the ½ symbol frequency component, and outputs thecorrelation value as an orthogonal correlation signal; a vectorcombination selecting unit that compares the magnitudes of the in-phaseand orthogonal correlation signals, matches the direction of a vectorobtained from the in-phase or orthogonal correlation signals whicheveris smaller to the direction of a vector obtained from the in-phase ororthogonal correlation signals whichever is larger, combines thesesignals, and outputs a correlation signal after the combination as acombined correlation signal; a preamble detecting/timing phasedifference calculating unit that calculates a vector angle and a vectorlength of the combined correlation signal, decides that the preamblesymbol has been detected when the vector length is larger than apredetermined threshold value, calculates a timing phase differenceusing a vector angle shown by the combined correlation signal at thattime, and outputs a phase control signal; wherein said preambledetecting/timing phase difference calculating unit calculates a timingphase difference from a vector angle shown by a value obtained bymultiplying a sign {±1} of the in-phase component to a square root of anabsolute value of an in-phase component of a combined correlation signaland a value obtained by multiplying a sign {±1} of the orthogonalcomponent to a square root of an absolute value of an orthogonalcomponent of the combined correlation signal; and a data deciding unitthat extracts Nyquist point data from the digital base band signal usingthe regeneration symbol clock, decides the extracted Nyquist point data,and outputs the data as demodulated data.
 38. A demodulator comprising:an antenna that receives a radio signal; a frequency converting unitthat converts the frequency of the received radio signal into thefrequency of a base band signal; an A/D converting unit that convertsthe base band signal into a digital base band signal based on a samplingat two times a symbol rate using a regeneration sample clock; a timingregenerating device including: an in-phase component square calculationunit that receives a base band signal having a preamble symbol,calculates square of an in-phase component of the base band signal andoutputs the squared in-phase component; an in-phase multiplier thatmultiplies a sign bit (±1) of the in-phase component of the base bandsignal to the squared in-phase component and outputs the result assigned squared in-phase component; an orthogonal component squarecalculation unit that receives the base band signal, calculates squareof an orthogonal component of the base band signal and outputs thesquared orthogonal component; an orthogonal multiplier that multiplies asign bit (±1) of the orthogonal component of the base band signal to thesquared orthogonal component and outputs the result as a signed squaredorthogonal component; an adder that adds the signed squared in-phase andorthogonal components to generate a squared addition signal, and outputsthe squared addition signal; a subtracter that subtracts the signedsquared in-phase component from the signed squared orthogonal componentor vice versa to generate a squared subtraction signal, and outputs thesquared subtraction signal; a squared-addition signal componentcorrelation calculating unit that calculates a correlation value betweenthe squared addition signal and a ½ symbol frequency component, andoutputs this correlation value as an addition correlation signal; asquared-subtraction signal component correlation calculating unit thatcalculates a correlation value between the squared subtraction signaland the ½ symbol frequency component, and outputs this correlation valueas a subtraction correlation signal; a vector selecting unit thatcompares the magnitudes of the addition and subtraction correlationsignals, selects the addition correlation signal or the subtractioncorrelation signal whichever is larger, and outputs this signal as aselected correlation signal; a timing phase difference calculating unitthat outputs a phase control signal from a vector angle shown by theselected correlation signal; a VCO that outputs a regeneration symbolclock, a regeneration sample clock, and the ½ symbol frequencycomponent, based on the phase control signal, wherein the base bandsignal to be input into the in-phase component square calculation unitand the orthogonal component square calculation unit is a signal thathas been sampled based on the regeneration sample clock, saidsquared-addition signal component correlation calculating unitcalculates the correlation value using the ½ symbol frequency componentoutput from said VCO, said squared-subtraction signal componentcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said VCO; and a data decidingunit that extracts Nyquist point data from the digital base band signalusing the regeneration symbol clock, decides the extracted Nyquist pointdata, and outputs the data as demodulated data.
 39. A demodulatorcomprising: an antenna that receives a radio signal; a frequencyconverting unit that converts the frequency of the received radio signalinto the frequency of a base band signal; an A/D converting unit thatconverts the base band signal into a digital base band signal based on asampling at two times a symbol rate using an asynchronous sample clock;a timing regenerating device including: an in-phase component squarecalculation unit that receives a base band signal having a preamblesymbol, calculates square of an in-phase component of the base bandsignal and outputs the squared in-phase component; an in-phasemultiplier that multiplies a sign bit (±1) of the in-phase component ofthe base band signal to the squared in-phase component and outputs theresult as signed squared in-phase component; an orthogonal componentsquare calculation unit that receives the base band signal, calculatessquare of an orthogonal component of the base band signal and outputsthe squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; a squared-preamble in-phasecorrelation calculating unit that calculates a correlation value betweenthe signed squared in-phase component and a ½ symbol frequencycomponent, and outputs the correlation value as an in-phase correlationsignal; a squared-preamble orthogonal correlation calculating unit thatcalculates a correlation value between the signed squared orthogonalcomponent and the ½ symbol frequency component, and outputs thecorrelation value as an orthogonal correlation signal; a vectorcombination selecting unit that compares the magnitudes of the in-phaseand orthogonal correlation signals, matches the direction of a vectorobtained from the in-phase or orthogonal correlation signals whicheveris smaller to the direction of a vector obtained from the in-phase ororthogonal correlation signals whichever is larger, combines thesesignals, and outputs a correlation signal after the combination as acombined correlation signal; a timing phase difference calculating unitthat outputs a phase control signal from a vector angle shown by thecombined correlation signal; wherein said timing phase differencecalculating unit calculates a timing phase difference from a square rootof the in-phase component and the vector angle of a square root of theorthogonal component of the combined correlation signal; a datainterpolating unit that interpolates the digital base band signal thathas been sampled by the asynchronous sample clock, and outputs theinterpolated data as an interpolated base band signal; and a datadeciding unit that extracts a Nyquist point of the interpolated baseband signal based on a phase control signal, decides data at theextracted Nyquist point, and outputs the data as demodulated data.
 40. Ademodulator comprising: an antenna that receives a radio signal; afrequency converting unit that converts the frequency of the receivedradio signal into the frequency of a base band signal; an A/D convertingunit that converts the base band signal into a digital base band signalbased on a sampling at two times a symbol rate using the asynchronoussample clock; a timing regenerating device including: an in-phasecomponent square calculation unit that receives a base band signalhaving a preamble symbol, calculates square of an in-phase component ofthe base band signal and outputs the squared in-phase component; anin-phase multiplier that multiplies a sign bit (±1) of the in-phasecomponent of the base band signal to the squared in-phase component andoutputs the result as signed squared in-phase component; an orthogonalcomponent square calculation unit that receives the base band signal,calculates square of an orthogonal component of the base band signal andoutputs the squared orthogonal component; an orthogonal multiplier thatmultiplies a sign bit (±1) of the orthogonal component of the base bandsignal to the squared orthogonal component and outputs the result as asigned squared orthogonal component; a squared-preamble in-phasecorrelation calculating unit that calculates a correlation value betweenthe signed squared in-phase component and a ½ symbol frequencycomponent, and outputs the correlation value as an in-phase correlationsignal; a squared-preamble orthogonal correlation calculating unit thatcalculates a correlation value between the signed squared orthogonalcomponent and the ½ symbol frequency component, and outputs thecorrelation value as an orthogonal correlation signal; a vectorcombination selecting unit that compares the magnitudes of the in-phaseand orthogonal correlation signals, matches the direction of a vectorobtained from the in-phase or orthogonal correlation signals whicheveris smaller to the direction of a vector obtained from the in-phase ororthogonal correlation signals whichever is larger, combines thesesignals, and outputs a correlation signal after the combination as acombined correlation signal; a preamble detecting/timing phasedifference calculating unit that calculates a vector angle and a vectorlength of the combined correlation signal, decides that the preamblesymbol has been detected when the vector length is larger than apredetermined threshold value, calculates a timing phase differenceusing a vector angle shown by the combined correlation signal at thattime, and outputs a phase control signal; a clip detecting unit thatreceives the base band signal having a preamble symbol, converts boththe in-phase and orthogonal components of the base band signal into “0”when at least one value of the in-phase and orthogonal components of thebase band signal is outside a predetermined range, and outputs the baseband signal straight when at least one value of the in-phase andorthogonal components of the base band signal is within thepredetermined range, wherein the base band signal to be input into saidin-phase component square calculation unit and said orthogonal componentsquare calculation unit is the base band signal output from said clipdetecting unit; a data interpolating unit that interpolates the digitalbase band signal that has been sampled by the asynchronous sample clock,and outputs the interpolated data as an interpolated base band signal;and a data deciding unit that extracts a Nyquist point of theinterpolated base band signal based on a phase control signal, decidesdata at the extracted Nyquist point, and outputs the data as demodulateddata.
 41. A demodulator comprising: an antenna that receives a radiosignal; a frequency converting unit that converts the frequency of thereceived radio signal into the frequency of a base band signal; an A/Dconverting unit that converts the base band signal into a digital baseband signal based on a sampling at two times a symbol rate using anasynchronous sample clock; a timing regenerating device including: anin-phase component square calculation unit that receives a base bandsignal having a preamble symbol, calculates square of an in-phasecomponent of the base band signal and outputs the squared in-phasecomponent; an in-phase multiplier that multiplies a sign bit (±1) of thein-phase component of the base band signal to the squared in-phasecomponent and outputs the result as signed squared in-phase component;an orthogonal component square calculation unit that receives the baseband signal, calculates square of an orthogonal component of the baseband signal and outputs the squared orthogonal component; an orthogonalmultiplier that multiplies a sign bit (±1) of the orthogonal componentof the base band signal to the squared orthogonal component and outputsthe result as a signed squared orthogonal component; an adder that addsthe signed squared in-phase and orthogonal components to generate asquared addition signal, and outputs the squared addition signal; asubtracter that subtracts the signed squared in-phase component from thesigned squared orthogonal component or vice versa to generate a squaredsubtraction signal, and outputs the squared subtraction signal; asquared-addition signal component correlation calculating unit thatcalculates a correlation value between the squared addition signal and a½ symbol frequency component, and outputs this correlation value as anaddition correlation signal; a squared-subtraction signal componentcorrelation calculating unit that calculates a correlation value betweenthe squared subtraction signal and the ½ symbol frequency component, andoutputs this correlation value as a subtraction correlation signal; avector selecting unit that compares the magnitudes of the addition andsubtraction correlation signals, selects the addition correlation signalor the subtraction correlation signal whichever is larger, and outputsthis signal as a selected correlation signal; a timing phase differencecalculating unit that outputs a phase control signal from a vector angleshown by the selected correlation signal; a VCO that outputs aregeneration symbol clock, a regeneration sample clock, and the ½ symbolfrequency component, based on the phase control signal, wherein the baseband signal to be input into the in-phase component square calculationunit and the orthogonal component square calculation unit is a signalthat has been sampled based on the regeneration sample clock, saidsquared-addition signal component correlation calculating unitcalculates the correlation value using the ½ symbol frequency componentoutput from said VCO, said squared-subtraction signal componentcorrelation calculating unit calculates the correlation value using the½ symbol frequency component output from said VCO; a phase detectingunit that detects advancement/delay of a timing phase using the baseband signal sampled based on the regeneration sample clock, and outputsdetected signals as phase detection signals; a phase detection signalaveraging unit that calculates an average of the phase detectionsignals, and outputs the average as a phase advance/delay signal,wherein said VCO outputs the regeneration symbol clock, the regenerationsample clock, and the ½ symbol frequency component, based on the phasecontrol signal and the phase advance/delay signal; a data interpolatingunit that interpolates the digital base band signal that has beensampled by the asynchronous sample clock, and outputs the interpolateddata as an interpolated base band signal; and a data deciding unit thatextracts a Nyquist point of the interpolated base band signal based on aphase control signal, decides data at the extracted Nyquist point, andoutputs the data as demodulated data.